Growing vegetables in greenhouses

The thing with vegetables is that most of them do not grow throughout the year. Vegetables need sunlight – that is the law of nature. That is the nature of mother earth. When winter approaches, the greenery vanishes losing the hopes of most budding gardeners. Winter, so to say, is considered the enemy of the gardeners. But you can change this phenomenon a little bit with a greenhouse. Although a greenhouse is a costly enterprise, it is the ideal solution to grow vegetables even in harsh climates such as winter.

Enter winter, and most people tend to neglect their gardening. That is the most unwise thing to do. You should never let your gardening go astray just because winter has arrived. If you look around a little closer, you will come across quite a few winter vegetables that will sustain even the coldest season. Growing vegetables in winter will offer you benefits as well. You can extend the season while most vegetables grown in winter produces early crops much better than spring and other falls.

What you simply need is a little preparation from late spring and early summer. You can try out winter vegetables such as winter cabbage, Brussels sprouts and kale towards late spring. Even if you could not get yourself to do some gardening early summer, do not worry. Winter is not that harsh. You can still do gardening during the winter.

The winter cabbage comes in different varieties. The best variety can tolerate harsh cold climates. These cabbages are known for their tiny, yet tough, heads. Some popular varities include OS Cross, Huron and Danish Ball Head.

Best is if you can sow seeds straight into a bed while it is still summer. It could be even late summer. You need to grow it before winter knocks at your doorstep. The seeds can take a root even when it is under 40 degrees of Fahrenheit. Keep on sowing on a weekly basis for then it will sustain winter.

But remember not expose the young leaves to frost. You do not have to worry much about watering them, because the winter crops have their moisture deposited by nature.

Most vegetables you buy in the supermarket or an annual are usually grown in that manner.

Tomato is considered a permanent vegetable. They can grow any time around the year. Throughout its life, the plant will provide fresh tomatoes. However, any farmer would tell you the issue with tomato. That plant is mostly a tropical one. Which means you cannot grow it in the winter. But then that’s why you bank on a greenhouse. Or simply put them in a container that you can easily move during the winter.

Peppers are another plant family that you can permanently plant. Like tomatoes, peppers are mostly grown in tropical climates. This could be overcome if you have a proper greenhouse with a varieties such as Habaneros which can withstand harsh weather conditions.

Eggplant is another vegetable that could be grown year round in a greenhouse. You will be able to look forward to the harvest on a yearly basis.

Garlic is another plant that could be grown year round, but earned notoriety as a plant because it takes such a long time to harvest. All the same, it pays you well for waiting. But it grows quite easily.

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When most people think about greenhouse gardening they think extra heat for tomatoes & peppers.

Greenhouse Gardening is about so much more! While we grow warm season crops in our greenhouse during the summer months, we also love growing cool season crops in the spring and sowing cold hardy crops for the fall and winter garden.

Today I wanted to share our experience unheated greenhouse gardening to grow vegetables year-round.

I’m really excited to share this post with you today on Greenhouse Gardening: Growing Vegetables Year-Round

In this post, I’ll share with you tips for gardening in a greenhouse and the mistakes we made that you shouldn’t. I will also tell you all the crops we grow in our greenhouse year-round and show you the seasonal flow of our year.

We’ll see the greenhouse garden empty, with fall & winter crops, overwintered greens & seedlings in the spring, warm season crops in the summer and back again to the fall and winter crops.

Some information before we get started about our greenhouse.

  • Our gardening zone is 5b.
  • We live in the Canadian mountains.
  • It reaches as low as -20C/-4F.
  • This is an unheated greenhouse with no supplementary light
  • We moved onto this land and the greenhouse was already here. I wish I could give you the exact details of the structure and greenhouse cover but I can’t.
  • The cover is a thicker canvas and not clear. I’ve tried to find the source for this cover but I’ve yet to find it. We plan on changing the cover to greenhouse plastic in the coming years.
  • This greenhouse has held impressive amounts of snow. I’m not sure if it was the canvas played a factor in this but there were times (because I was pregnant our first winter using it) that we didn’t get outside as often to clear the snow. That winter we’d had the most snow in years. No damages that year thankfully!
  • There are two air vents a the top that spin and two doors on either side of the greenhouse for venting. I would love the vents that roll up the side and when we change the greenhouse plastic I might just see if that’s something we can do.

We used mini hoop tunnels and low tunnels until we moved to this acreage and had a greenhouse. You can learn more about fall and winter gardening without a greenhouse from previous posts I’ve written.

  • Ultimate Guide to Fall & Winter Gardening
  • Fall and Winter Garden Plans
  • Grow 365 Days a Year
  • How to Plant your Fall & Winter Garden
  • Crops that can Handle Frosts and Snow
  • Growing food Year-Round in a Greenhouse
  • Zucchini Blossom End Rot

Greenhouse Gardening: Growing Vegetables Year-Round


I will begin this post with fall when I first cleared it out. When we moved onto the acreage at the end of August the inside of the greenhouse had been left for a couple of years and it became a jungle.

Literally a jungle of weeds!

Scary right?

I cleaned it up as best I could, as you can see in the photos below, but I knew we were facing a massive amount of weed seeds in there.

Planting fall crops was something I still did. Even just to observe the unheated greenhouse and to overwinter greens.

I sowed winter lettuce (winter density), kale, spinach, mustard greens, and turnips.

However, the slugs in the greenhouse were an epidemic!

We lost a lot of crops, we’re dealing with huge amount of weed seeds and I was pregnant. Oh boy! Below you can see the progression of October and November and it wasn’t a total failure, we did get some harvests and I managed to pay a lot of attention of what crops were doing well in an unheated greenhouse. Observation is an underrated attribute to gardening, it helps you learn and grow as a gardener and understand your microclimate better.

Once November hit we had a decent amount of greens.

These crops were sown in late September, later than I wanted them to be as I prefer early Sept, but the Komatsuna, Tatsoi, Spinach, and Kale did great even if there were weeds all over and in between. I failed to thin out the seedlings so they would have done better if I had. Here’s a list of cold hardy crops for you to grow.


January & February when temps dipped to -20C/4F the greens were in a heavy frost.

Many rebounded though to harvest when thawed and certain crops overwintered.

Constant snow removal is imperative.

We hadn’t had this much snow in years (even though it used to be the norm here in the Canadian mountains, the climate has definitely created milder winters since I’ve been gardening 8 years ago). We made the mistake of not having enough path space around the edges of the greenhouse. Next year we plan on having a better snow removal system. How do we reach the top? We tap it on the inside with a broom and it slides down the sides, then we remove it from the sides.

Snow removal is definitely a workout!


In the spring I didn’t think many of the crops had survived well enough to provide us with overwintered greens. I pulled and cleaned out most of the greenhouse as there was a weed in there that was thriving. Later I discovered it was the edible Claytonia! However I didn’t want a whole greenhouse of it, and edible or not, I wanted other crops. I weeded, amended the beds and sowed spring crops: mustard greens, lettuce, spinach, radishes, turnips, arugula.

The overwintered kale looked dull and unhealthy then rebounded with a ton of fresh kale!

Below you can see it in March, April then thriving in May before it finally bolted and tried to flower.

In the spring we enjoyed a decent amount of harvests although it should have been more with we were still dealing with a lot of weeds. I sowed most of the crops end of March, then again in April and even early May.

This is succession sowing meaning sowing multiple times over a period of weeks instead of all at once.

It helps you to figure out the best time, and because the weather is unpredictable in the spring it increases crops success rate. You can learn more about succession sowing here and also in my garden planning book.

One mistake I made was mulching our greenhouse!

In our location, we have A LOT of meadow voles and our mulched greenhouse to suppress weeds became a haven for them when it was still snowy outside. As soon as I moved the mulch and took other rodent-repelling measures, they cleared out but they ate most of my beautiful seedlings. Onto summer crops then!


I grew tomato, pepper and eggplant seedlings inside our home (basement with sunblaster grow lights). I transplanted them mid-May and again end of May.

Our greenhouse cover is fantastic for snow weight as it’s currently a canvas, however, I do believe it must inhibit some light transmission.

Our warm season crops did great though, especially the peppers. The tomatoes I didn’t prune and trellis as well as I should have (Preggy! Our baby was born mid-July so my gardening efforts were greatly diminished). All in all we had great tomato and pepper yields for our summer greenhouse garden.

*Fall Again*

By early September I had cleared most of the pepper and tomato plants, amended the soil with compost & azomite and sowed fall crops. They were succession planted from early to late September as I would leave certain rows of tomatoes to ripen further.

The photos below were taken today (end of September) and you can see that the first bed that I sowed is full of greens which I was thinning out today. The other 4 beds are growing slowly and whether or not those crops will grow to become full-sized will depend on our fall and winter temps. Most gardeners in our area have stopped gardening for the season so it was nice to harvest a big basket of greens and micro greens (from thinning out our crops).

I look forward to seeing how these fall crops will do over the winter months.

Updated: See our successful second winter using the unheated greenhouse for harvests!

My name is Isis Loran, creator of the Family Food Garden. I’ve been gardening for over 10 years now and push the limits of our zone 5 climates. I love growing heirlooms & experimenting with hundreds of varieties, season extending, crunchy homesteading and permaculture.

If you want to have veggies all the year-round and you’re not afraid of a bit of work, growing vegetables in a greenhouse may be just right for you. Managing a greenhouse takes quite a bit of monitoring, and you must be ready and able to provide heating during the cold months (check my reviews of best greenhouse heaters) and shade and ventilation during the warmer months.

It’s also important to understand what plants need to thrive in nature and to replicate those conditions as closely as possible.

In this article, I provide an overview of greenhouse growing along with sound advice to help you succeed. Read on to learn more.

Types of Greenhouses

As you plan your greenhouse, you may be baffled by some of the terminology you come across. For example, it may seem that there are three entirely different types of greenhouse structure or that you need to set up three separate greenhouses. This is not the case, but there are three different ways to keep your greenhouse, depending upon the temperature range you are able to maintain.

1. Cold greenhouse: This type of greenhouse is warmed by the sun’s rays (passive solar energy). It gets as warm as the sun will allow it during the daytime and may drop to around -2 Celsius overnight. This is a good place to over-winter your non-frost-sensitive plants.

2. Cool greenhouse: This type of greenhouse is heated artificially during the winter, but it is not kept “hothouse” warm. You’ll want to maintain a temperature of about 15C during the day and 7C or above overnight. This is a good place to keep established, frost sensitive plants during the winter.

3. Warm greenhouse: This is where you start new seedlings, keep your exotic plants and grow hothouse tomatoes and such. This type of greenhouse stays well heated all winter through. The temperature should not drop below 12-13C overnight and can be quite warm during the day thanks to a combination of artificial heating and passive solar energy.

Heating & Ventilation Pose Challenges

When winter is over, you’ll need to protect your plants from the excessive heat that will surely build up inside your greenhouse. A greenhouse can become very hot (40+ degrees) very quickly if it is kept shut up on a bright, sunny day. This causes some plants (e.g. tomatoes) to stop growing. It can kill others.

To provide good ventilation and cooling, you must have windows and/or vents and fans to bring in fresh air and remove stale air. Provide shade with shade cloths or establish your greenhouse near deciduous trees which leaf out and provide shade during the summer months.

What are the Best Veggies for Greenhouse Growing?

You can grow all your favourite veggies in a greenhouse, but some may be a bit trickier than others. Study the types of vegetables you wish to grow so that you can carefully set up the right balance of sunlight, water and warmth to produce healthy, tasty produce. If you do not provide enough light, or if you try to grow your veggies at the wrong temperature, they may end up flavorless.

Some of the best choices in greenhouse veg include:

  • Cucumbers
  • Tomatoes
  • Eggplant
  • Peppers
  • Melons
  • Squash
  • Carrots
  • Lettuce
  • Radish
  • Beans

When you select your seed, seek out varieties that have been specially developed for greenhouse growth. These perform better than your average garden variety seeds.

Tips for Tomatoes

Most tomatoes do well grown in a warm greenhouse. “Tornado” is a compact variety that does especially well in this environment. The heat and humidity are made to order for them. Just keep in mind that extreme heat prevents tomatoes from bearing fruit. Try to keep the temperature below 32C with good ventilation and shade as needed (you will need a reliable greenhouse thermometer).

If you are keeping a cool greenhouse, try “Alicante”. This variety is especially developed to withstand cooler temperatures.

Grow a Lettuce Patch

All types of lettuces do well in a cool greenhouse setting, but with protection from excessive heat, they can do well in a warm greenhouse. Too much heat results in bitter lettuce. Place your lettuce in an area that receives indirect light and provide shade and ventilation as needed.

Your Cucumber Vine Can Provide Shade

Cucumbers do very well as container plants in a greenhouse. They grow vigorously growing quickly clamber up a trellis. This habit makes them a good space saver and a good companion for shade seeking plants such as lettuce.

Peppers Love the Heat

All kinds of pepper plants do very well in a warm greenhouse setting. Most types are fairly compact and easy to grow in containers. They are fast growing and usually very prolific.

Start Squash Plants

Most types of squash and pumpkins tend to spread out and ramble with wild abandon, so they are not good choices as permanent greenhouse residents. It is a good idea to start your seeds indoors early so that your plants can have the best chance of maturing and producing well in your garden.

Growing Vegetables in a Greenhouse Year Round

With a good greenhouse, you have complete control over the climate, so you can grow your veg all year round. You should harvest frequently because mature vegetable plants tend to be too big for indoor growing. Allocate your space well so that you can have one or two areas in different levels of production at all times.

To plant multiple harvests of plants raised to maturity indoors, carefully study the requirements of each type of plant you want. Choose varieties that have similar requirements and strive to keep your greenhouse at ideal temperature, light and humidity levels for the plants you have chosen.

If you also have an outdoor garden, expand your production by starting seeds indoors in the late winter and transplanting them outdoors after all danger of frost has passed.

What’s the Best Time to Start Seedlings for Transplant?

Use your best judgment and the advice of experienced local gardeners to determine the perfect times for starting your seedlings for outdoor transplant. Every area is different, so it pays to take your time and to befriend members of local garden societies and others who may be able to share a wealth of good information.

If you are starting tomato seeds in a warm greenhouse and plan to transplant them outdoors, generally speaking you should start your seeds early in January. They should be ready to move from small pots to 5 gallon buckets or grow bags by late February or early March.

Once you have transplanted them, place the containers on the south side of your greenhouse for maximum sun exposure. If you use 5 gallon buckets, they can stay indoors if you wish. Otherwise, transplant them to your garden after all danger of frost has passed.

You should see ripe tomatoes by mid June. You can start new tomato seeds in July to have a fresh crop in the winter time.

Start your cucumber and pepper seeds late in February and transplant them into 5 gallon buckets kept on the south side of your greenhouse (or into your garden) in April to harvest late in June.

TIP: At transplanting time, your young plants will need support. Use bamboo stakes, tomato cages or similar structures to provide support. Secure the stems with loosely tied, soft, thick twine or old nylon stockings. A tie that is too thin or too tight will damage delicate stems.

Pollination & Pest Control

Lack of pollinators (bugs, bees and butterflies) in your greenhouse can cause you to have lots of pretty leaves but no fruits and veggies. With no natural pollinators, you will need to perform pollination tasks yourself. Fortunately, this does not involve flitting about from blossom-to-blossom with collected pollen in your cargo pockets.

For most plants, you can spread pollen by shaking the plant gently a couple of times during its flowering time. For tomato plants, tap on their support structures (bamboo stake, tomato cage, etc.) in the morning and in the evening when you see that flowers’ tiny petals have curved back. Your window of opportunity for this is small (3 days) so keep a close eye on your tomato blossoms.

If all this sounds a bit arduous, you’ll be happy to know that you can turn to ladybugs for natural assistance. These jaunty little red and black beetles make a charming addition to your greenhouse, and they are quite efficient as pollinators. In fact, beetles make up the largest group (collectively) of pollinators.

Ladybugs can stay quite happy in your greenhouse garden trundling about from plant to plant drinking nectar and eating pollen. Like most beetles, they are especially fond of blossoms that are green or off white and produce a lot of pollen (e.g. tomato blossoms).

In addition to being good pollinators, ladybugs are also excellent pest controllers. They eat all manner of tiny sap-feeding insects – especially aphids. In fact, a single ladybug can polish off as many as fifty aphids in a day.

Using ladybugs to control pests is a great idea for an indoor, organic garden because they are quite efficient and can keep your garden relatively pest free without the use of any dangerous pesticides. You can purchase young ladybugs from your local garden center or online to release into your indoor garden.

These cute little garden dwellers will live a year or two, and in the course of their lifetime, they will reproduce many times over, so you may only have to buy them once. If you end up with a ladybug population explosion, you can gather up the extras and relocate them to your yard or garden in mild weather, or share them with a fellow gardener.

How to Introduce Ladybugs to Your Indoor Garden

It’s a good idea to release them just before dark and just after you have misted your plants. When you release them, they will be thirsty so they will want to stay on your plants and drink the mist you have provided. As the sun goes down, they’ll settle in for the night. The next morning, they’ll wake up and feel that they are home, so you won’t have any problem with them flying off to seek greener pastures.

TIP: Be careful if you have a pet bird or lizard. Don’t let it roam loose near plants with lady bugs because they are poisonous to birds and reptiles. While wild birds and reptiles are probably wise to this, domesticated creatures might not be.

Is All the Effort Really Worth It?

Maintaining a warm or cool greenhouse can be a bit financially challenging. Heating is not cheap, and if you have a long, cold winter season you may need to seriously weigh the cost of veggies against the cost of heat. Do consider the fact that a greenhouse doesn’t just provide you with fresh veggies, though. It also provides you a pleasant, cozy place to escape and recreate and the opportunity to spend time with fresh, green, living plants in the dead of winter.

Having a steady supply of natural, organic produce is a big plus in today’s world. If your growing season is very short, and/or if you are located in an area where fresh produce is in short supply, a greenhouse can be a source of good food and maybe even a bit of money. If you grow enough produce, you may be able to share it with or sell it to your friends and neighbours.

Greenhouse, Garden & Allotment Blog

It’s exciting when you begin to explore the opportunities that are available for growing plants or vegetables in a greenhouse.

Whether you have toyed with the idea or you’re ready to jump in and start, we’ve put together a basic guide for growing vegetables in a greenhouse for beginners.

Buying a greenhouse

There are thousands of greenhouses to choose from and the choice is entirely yours, however, if you are new to gardening or greenhouses, perhaps consider choosing a smaller one to begin with.

You could start with an Ultimate Spacesaver Greenhouse, a small, manageable greenhouse ideal for beginners or people who don’t have much space in their garden or a bigger one such as the 4x6ft
Ultimate Greenhouse to get you started. It totally depends on what you want to achieve and how much you want to invest in your project.

One thing you don’t want to do is overwhelm yourself and
lose interest in your project because it seems too hard.

Where to build your greenhouse

Once you have purchased your greenhouse, the next thing you need to think about is where you are going to build it. Ideally, you need a spot which has maximum sun exposure but sheltered from cold winds.Another thing to take into consideration is having easy access to water and electricity.

What to grow your plants & vegetables in

For beginners, if you have a greenhouse with a soil floor, its best to start growing in ground soil, it will be easier to manage watering and fertilisation, however growing in containers, grow bags or bulb crates have their advantages, no weeding and reduced cases of soil borne diseases.

Again, the choice is yours.

What will you be growing?

Knowing what you are going to grow is one of the first steps to getting started in your greenhouse. Before you choose the plants and crops you want to grow, research what environments, temperatures and humidity your plants and crops will need to thrive.

Try not to overstock the greenhouse at the beginning of your journey, overcrowding plants can cause the plants & vegetables stress as the lack of space will make them unable to produce properly.

We have listed a few easy to grow vegetables to help get you started;

  • Salad leaves
  • Spring onions and radishes
  • Potatoes
  • Peas
  • Herbs
  • Broad beans
  • Runner beans
  • Onions and garlic
  • Tomatoes
  • Beetroot
  • The list goes on.

Understand your growing temperatures

Get a thermometer. It will be the most invaluable item you own whilst growing in your greenhouse.

You will need to research what temperature to keep your greenhouse for the type of plants/vegetables you are growing as some will need more heat than others so be sure to check the temperature and humidity regularly in your greenhouse.

It’s imperative to keep the greenhouse at the right temperature so your plants and vegetables grow in full.

A little research into heaters, vents and fans will go a long way when getting the temperature right for your greenhouse. It’s best to get a good understanding of what’s involved when controlling the temperature and humidity throughout the seasons.

Light and space in the greenhouse

Your greenhouse should get enough natural light for your plants and crops to grow during late spring and summer but if you want to continue to grow in Autumn and Winter you may need to consider purchasing extra lighting.

There are hundreds of grow lights available, LED grow lights tend to be the most popular however if you are in a smaller greenhouse or growing a smaller crop, a normal fluorescent strip can be hung 3-7 inches above the plants.

Make sure your plants and crops have enough space to breathe. Plants which are touching each other tend not to grow as well and it encourages the spread of disease.

Caring for your plants & vegetables

Once you have the temperature and humidity under control in your greenhouse, the most important part to keep your plants and crops happy and healthy is water! Investing in a water-butt to collect rainwater is a great source of water for your plants.

Don’t go water mad though, some crops will need more than others and you will need to keep an eye out on plant size and temperature. Try not to cause too much splashing when watering your crops, this is to avoid the spread of diseases.

Keep an eye out for bugs, slugs and other nasty little critters, many people choose to slug watch before they leave the greenhouse for the night. Keeping your greenhouse clean and tidy also helps with pest control.

There you have it, from selecting your greenhouse to caring for your crops, we hope you enjoyed reading our article on growing vegetables in a greenhouse for beginners.

Every home gardener dreams about owning a backyard greenhouse, which provides the perfect environment for starting plants from seed and growing flowers and vegetable plants. A greenhouse also allows you to get a head start on spring planting and to extend the growing season well into the autumn.

The problem is that traditional greenhouses are quite expensive and typically too large for the average backyard. Fortunately there are two do-it-yourself options: buy a ready-to-assemble greenhouse kit or purchase plans and build the greenhouse from scratch. (Note that free downloadable plans are also available from various online sources.)

There are a lot of things to consider before choosing the greenhouse that’s right for you. Such as:

Local Ordinances

Check with your town’s building department to make sure you’re even allowed to build a greenhouse on your property. Greenhouses are typically considered outbuildings, so you’ll have to apply for a building permit. And if you live in a community with a homeowner’s association (HOA), you’ll have to get approval from the HOA, which might be difficult because many housing communities have a strict no-outbuildings covenant.

Orientation to the Sun

Since the object of a greenhouse is to provide a warm, sunny spot for your plants, it’s important that it be situated properly in your yard. Optimal greenhouse orientation is facing south or southeast in order to capture the early-morning sun. An east-facing orientation works well in most climates, too.

Try to pick a location that receives at least six hours of uninterrupted sun per day. If you live in a region that receives significant snowfall, be sure the snow-load rating of the greenhouse can support a blanket of snow without collapsing.

Glazing Options

Glass is the most traditional glazing material for greenhouses. But glass is heavy, fragile and expensive, so most DIY greenhouses are glazed with polycarbonate, acrylic, fiberglass, or polyethylene sheeting.

Panels of polycarbonate, acrylic and fiberglass are resilient, good insulators and have excellent light transmission, although fiberglass can discolor over time. Polyethylene sheeting is very affordable and easy to install, but it’s not very tough and can be easily punctured and damaged.

Frame Materials

A majority of greenhouse frames are made of wood or metal. Wood is less expensive, easier to work with and suitable for small- to medium-size greenhouses. Metal is stronger and more weather resistant than wood, but it’s costlier. Aluminum is a good choice because it’s lightweight, corrosion resistant, and strong.

Floor Materials

The floor of a greenhouse can be made of any number of materials, including gravel, wood decking, flagstone, metal grates, poured concrete, or just bare dirt. Keep in mind, however, that a dirt floor is only practical if your yard stays bone-dry, otherwise it’ll become a muddy quagmire.

Concrete is extremely durable, but it’s relatively expensive to pour and it doesn’t drain well. A gravel floor is inexpensive, drains well, and can easily be refurbished by simply adding more gravel.

Temperature Regulation

Being able to regulate the temperature inside the greenhouse is critical because it can get stiflingly hot in summer or bitterly cold in winter. To expel hot air, use operable windows, rooftop vents or exhaust fans. And use shade cloths to block out solar heat gain.

When the weather turns cold, maintain a warm greenhouse by installing an electric heater that’s equipped with a thermostatically controlled fan. In moderate climates, passive solar systems can help chase away the cold. Fill barrels with water or stack concrete blocks inside the greenhouse; they’ll absorb the sun’s energy during the day and then release it as heat at night.

The Best Greenhouse Kits and Plans


Palram Harmony 6 feet x 8 feet Polycarbonate Greenhouse – This kit has a powder-coated metal frame, polycarbonate glazing, and roof-mounted vent.


Outsunny 20 feet x 10 feet x 7 feet Portable Walk-in Garden Greenhouse – Measuring a spacious 10 feet x 20 feet, this greenhouse kit has a steel frame and transparent plastic cover.


Handy Home Products Phoenix Solar Shed – Part greenhouse, part garden shed, this easy-to-assemble kit measures 8 feet x 10 feet and features an attractive salt-box roof.

Free plans for a compact DIY Greenhouse from Black & Decker.


You can view free plans to build this unique greenhouse, which features 2 x 4 framing and polycarbonate glazing, or pay $5 for an ad-free (and much easier to read) download.

Did you know that many winter vegetables can thrive in an unheated greenhouse garden?

Here in Northern Utah, a plastic-skinned, unheated greenhouse can get pretty cold at night. Consequently, not every type of plant can survive the plummeting temperatures. Some cold-hardy vegetables actually grow quite well in a winter greenhouse garden, however, providing a fresh bounty for your family’s table throughout the coldest of months.

Root Winter Vegetables Grow Well in Your Cold Weather Greenhouse

Did you know that the cold Utah winter temperatures can stimulate the sugar production in some root vegetables? This helps to protect their roots from freeze damage while giving them a delightful boost in sweetness.

Carrots, beets, radishes and turnips can all survive frosts and freezing temperatures. You can also plant onions and garlic with confidence.

But you don’t have to stick to the common root vegetables. Why not try planting leeks, parsnips or rutabagas in your unheated winter greenhouse? If you don’t typically leave room for these tasty varieties in your summer garden, a winter planting will give you a chance to experiment with new recipes.

Green Winter Vegetables to Consider for Your Unheated Greenhouse

Many types of leafy, green vegetables can thrive in a winter greenhouse.

Do you crave fresh salads during the winter months? Many varieties of lettuce are sensitive to freezing but some types, such as endive and radicchio, are rugged enough to tolerate the cold. Kale and Swiss chard can also grow quite vigorously in these conditions.

Spinach, arugula and cabbage are other options for tough plants that can survive a Utah winter. Likewise, collard and mustard greens grow well in an unheated greenhouse.

But what if you crave more than just leafy greens?

Plant some cold-hardy broccoli, celery or peas. Or, consider the always-popular option of Brussels sprouts. You could also start a permanent asparagus bed this year. You’ll have to wait a couple of years for your first harvest but you’ll have a new winter vegetable crop every year thereafter.

Tips for Good Winter Vegetable Growth in Your Greenhouse

Just as you would for an outdoor vegetable garden, you’ll need to space your plants properly to maximize growth.

If you prefer containers for planting your winter vegetables, space them far enough apart so that the plants’ leaves don’t touch. If you prefer raised garden beds in your winter greenhouse, make sure to thin out the weak plants as they grow. That way, the hardier plants have plenty of room to thrive.

If you notice any signs of disease in your winter vegetables, remove them promptly to prevent the problem from spreading. To keep pests under control, you may want to interplant some naturally-repellant marigolds. Or, you can purchase ladybugs and praying mantis egg cases, both of which are beneficial for greenhouse growing any time of the year.

As cold as it may be outside in Northern Utah, the temperature inside your greenhouse may be higher than you think during the day. On sunny days, it can become hot enough to stress some winter vegetables. To prevent any potential problems, make sure plenty of air is moving throughout the greenhouse space. Opening the doors can provide ventilation, or you may want to consider adding a fan.

In Salt Lake City, Millcreek Gardens has all of the indoor and outdoor plants and gardening supplies you need to grow a bountiful garden, winter or summer. Stop by and see us today to learn more about growing winter vegetables in Utah.

Greenhouse Vegetable Plants: Growing Vegetables In A Hobby Greenhouse

If you’re like most gardeners, you’re probably ready to get your hands on some dirt by the middle of winter. If you install a hobby greenhouse next to your home, you may be able to make that wish come true virtually every day of the year. Growing vegetables in a hobby greenhouse allows them to extend the season, sometimes by months, giving you a year-round gardening opportunity. While you can’t grow all vegetables in a greenhouse 12 months of the year, you can plant cool-weather vegetables and let them grow through the worst of the winter weather with a simple heating system installed.

How to Grow Vegetables in a Greenhouse

Greenhouse vegetable plants may end up growing faster and stronger than those grown in a traditional garden, because you will be giving them the ideal environment for growth. When it’s below freezing outside, passive solar collectors and small heaters can leave the interior of a greenhouse cool but perfectly liveable for most spring vegetables. In the heat of the summer, fans and other cooling units can protect tender plants from the scorching heat of a southern climate.

You can grow greenhouse vegetable plants directly in the soil inside the enclosure, but container gardening is a more efficient use of space. You can take advantage of all three dimensions by placing planters on shelves, using trellis systems for vine plants and hanging planters for smaller vines, such as cherry tomatoes and strawberries.

Winter Vegetable Growing

Growing winter veggies for greenhouses is possible because most cool-season plants can tolerate temperatures near freezing, as long as their soil isn’t muddy. Container gardening solves that problem by giving the plants a perfect mix of potting soil.

If you’re planning on winter vegetable growing when building your greenhouse, add a passive solar collector such as a wall of black-painted water jugs. This will collect solar heat during the day and reflect it into the greenhouse at night, helping to prevent freezing. Add an additional small heater, either propane or electric, for the coldest days of the year.

Once you have the greenhouse built, experiment with plant placement for the best growing conditions for each variety. Cool season plants such as peas, lettuce, broccoli, carrots and spinach all have slightly different needs, and moving them around in the enclosure is the best way to find what works best with each plant.

Growing vegetables is demanding in terms of temperature and relative humidity, as to induce certain phenological stages require specific temperatures and relative humidities. It is therefore interesting the use of greenhouses for production, especially for shortening the growing cycle, earliness of the crop and the posibility of growing when the climate of the area is not suitable.

Hightlight vegetable crops in greenhouses were: tomato and pepper, followed by cucumbers, courgettes and melon. Although we can find other vegetables grown in greenhouses.

So we can make the following classification:

Polytunnel greenhouses growing:

Intensive vegetables crops in climate crontrol require very technically advanced greenhouses for production with forced ventilation systems, heating systems and hydroponic systems for fertigation.

The greenhouses used for this production are:

  • Chapel Greenhouses
  • Gothic Greenhouses
  • Asymmetric or Tropical Greenhouses

These greenhouses perform a exhaustive climate control, and can provide the optimum conditions for each phenological stage of the crop.

Traditional greenhouses growing:

This type of culture is used when environmental conditions are not favorable for cultivation in certain periods or seasons, where the climatic requirements are more demanding than the climate of the area provided.

Greenhouses models:

  • Parral o flat greenhouses
  • Tunnel Greenhouses
  • Greenhouses Backbone Structures

Nethouse Growing:

The main goal of growing vegetables under mesh is the protection against unfavourable weather conditions, providing some protection against pests and precocity. The drawback lies in the climate control, since this kind of greenhouses only modify the weather conditions briefly, which are at the mercy of the weather in the area.

Which greenhouse is the most suitable for vegetables growing?

From the technical point of view the best reccomendation is Polytunnel Greenhouse production, which make possible better climate control and better control of pests and diseases.

Production system

Depending on the crop in question will have the following systems:

  • Soil Growing: plantings on the floor. This type of culture, eventually, leads to problems in the root of diseases due to the continuous production of the same species in a particular area.
  • Growing in bags or containers of substrate: eliminates the problem of soil depletion, since, depending on the type of substrate used, substrate cleaning tasks can be performed.
  • Pure Hydroponics grown: in containers or growing tables on nutrient solutions.
  • Trays Crop: normally used in nurseries.

Tip 10: How to Succeed with Greenhouse Gardening

To be successful with greenhouse gardening there are few other factors we’d like you to consider. Factors such as watering, soil quality, pests and maintenance can all influence your success. Hopefully you can use this guideline to help you with what to keep track of.


The soil you use in your greenhouse should have nitrogen, phosphorus, and potassium which are all needed to grow healthy plants and crops. You can purchase special greenhouse potting mixes at your local garden centre or nursery. Most plants grow well if your soil has a pH ranging from 6.2 – 6.8. You can determine the soil pH using a test kit available at your garden centre. Yearly additions of compost to your soil will also make its quality excellent for growing.


Regularly watering plants within a greenhouse is not necessary since the greenhouse builds up its own moisture system. The only time when you need to water is when the soil is dry. However, different plants have different needs and some plants need more water than others especially during the warmer seasons. The best thing is to use a moisture gauge to measure the moisture and humidity within the greenhouse. Whether you prefer to water by hand or use a drip irrigation system or a misting system, keep a journal of when to water certain plants and stick to that regimen.


Good maintenance of your greenhouse will help you with the success of your crops and plants. If transporting new plants from the outside into your greenhouse, make sure to check them for pests and/or diseases. In a humid climate, pests and diseases will thrive. Disease will quickly spread to your other plants and before you know it all your plants will be infected. When you harvest your crops, you also want to make sure you rinse all fruits and vegetables before bringing them into your house. This way you will keep any bugs away from entering your home.


Fruits such as peaches and grapes grow very well in greenhouses. They don’t require a lot of space. Vegetables such as tomatoes and eggplants do well also in a greenhouse environment. When growing anything in a greenhouse, make sure you check on when to sow it. Your local garden centre can provide this information as well as which varieties will perform best in a greenhouse environment.

Planting and growing are enjoyable tasks not only during spring and summer. For people who own a greenhouse, it can be a year-round joy. A greenhouse is your healthiest backyard investment for fresh produce throughout the whole year. We will show you what plants you can grow to enjoy greenhouse gardening in winter.

There are actually quite a lot of plants that germinate and grow in colder temperatures and that don’t need as many hours of daylight. This is crucial in the cold season in order to save on electric bills for heating and artificial light.

Table of content

  • Perfect timing is crucial
  • Greenhouse Gardening in Winter: What to Grow?
  • Winter Gardening Techniques
  • Basic Winter Accessories

Perfect timing is crucial

Timing and temperature are crucial to have a successful harvest. It will help achieve the best flavor and quality of your crops. Understanding the suitable growing period and the days to harvest will make a big difference between producing a thriving garden and missing out on garden yield. Remember to read the seed packets thoroughly. It is loaded with a lot of useful information.

Slow maturing crops

100 days

Middle maturing crops

55-70 days

Quick maturing crops

40 days

Beets Kale Lettuce
Cabbage Radish Bok Choi
Carrots Turnips Spinach
Onions Leeks Arugula
Parsnips Chards Endive

Greenhouse gardening in winter: What to grow?

Winter growing is achievable because most cool-season plants can stand the near freezing temperature. You can start with cool-weather vegetables and allow them to grow throughout the serious winter. So don’t just stare at those seeds and let’s start planting!


There are sturdy onion varieties that can be successfully planted even when the greenhouse is unheated. Below are some of the varieties to consider.

  • Shakespeare is a white onion variety that can be relied on to grow during the winter.
  • Electric is an excellent red variety.
  • Radar provides an appealing yellow-colored variety.


If you live in an area that experiences milder winter weather, planting peas directly to the ground and close to each other will give you larger quantities. One of the best pea varieties that have been proven to withstand the cold is Meteor.

Leafy veggies

Winter greens sweeten with the cool weather. Here are some examples of the healthiest cold-tolerant leafy winter crops to grow.

Lettuce favors the cold weather. It is an excellent fall and spring vegetable that can even survive the coldest climates.

The hardiest of all kale types are the Siberian types which are soft and possess a softer taste than other kales. True Siberian type is great because it keeps on offering leaves all winter.

Cold hardy herbs

Herbs enhance every meal. There are herbs that are sensitive to colder temperature. However, some of the most often used herbs can actually grow in colder climates.

Parsley is the hardiest of herbs. It decreases its growth in wintertime and can sometimes survive without some protection.

Chives are so easy to grow that even kids can do it. Plant the seeds in a pot and place it in a dark place.

Rosemary is a perennial herb. It can be planted any time of the year and is strong enough to protect itself against the icy cold weather. This herb can thrive completely all year round.

Mint is a flexible herb that will proceed to grow during winter. It is like a weed that grows wild and is challenging to get rid of.

Root crops

Root crops are also great winter plant ideas. You can set aside most of these root crops in the soil and just dig them up when needed. Some wonderful root crops to plant include rutabagas, leeks, radishes, turnips, beets, parsnips, and carrots.

Broad beans

Planting broad beans during winter time means young plants by the time early spring comes in. The best method is to plant them in beds inside the greenhouse. If the weather is still mild, placing the beds near the door means they can easily be seen and pollinated by bees.


Garlic comes in several varieties and planting them couldn’t be easier. They have a long growing season like onions.

Chesnok red is the variety to go for if you want to taste a fuller garlic flavor.

Wight Cristo should be the option if you want traditional garlic that is commonly used for cooking recipes.

Winter gardening techniques

As the temperature drops, plant production can be kept at a steady and continuous process when you have a greenhouse.

Here are some more tips and guidelines to have a flourishing and successful garden even in winter.

Choose the right plants

It is imperative that you choose the right plants when you plan to garden during the winter. Pick the ones that you know will be able to survive the extremely cold winter weather. Leafy greens and root vegetables are the ones to go for when you want a successful winter planting season. Think of raising plants with similar humidity, light and watering requirements together.

Clean and inspect the greenhouse

The harvest done in late summer and fall means that your greenhouse needs a thorough inspection and cleaning whether you plan to plant or not. A greenhouse in tiptop form should be all set before winter comes.

Repair and maintenance are also must-dos around the greenhouse before planning your next step towards winter planting. This will also lessen common pests and disease difficulties.

Planning humidity and heating control

Striking the right balance of temperature and humidity should be the best way which can be helped with dehumidifying systems and proper ventilation. You can try to plant closer together to form a microenvironment with better relative humidity.

Light it up

Proper lighting is another important factor to consider for the winter greenhouse. A shady greenhouse will not be an efficient environment for plants unless you are growing mushrooms that require a dark environment. LED lights in the correct spectrum are the most efficient way of implementing a bright and warm atmosphere for growing plants.

Seedlings need light for them to thrive and grow. During winter, grow lights are the things to have when you want healthy and robust seedlings. Have a look at these easy to use and power-efficient Grow Lights.

Basic winter accessories to get started

If you plan to continue gardening during the winter months, the first top investment should be a sturdy greenhouse with a proper insulation factor. Here are a few greenhouse accessories or equipment to either be built in or become benchmarks when you’re out on the market for a winter greenhouse.

Built-in benches and shelves

It would be a fantastic deal if you can get a greenhouse fitted with built-in racks and benches. They are important greenhouse equipment to have, not only for convenience but also serve as great storage spaces. Appreciate more planting capacity while taking up limited space. In winter, you don’t want to plant your crops in the ground. Shelves help your crops from freezing.


Plants need some light to photosynthesize in order to survive. The light demands to have equal wavelengths as our sun. That is the reason why a conventional light bulb will not work.

Incandescent lamps work good for raising houseplants, but they do not fit for an indoor setup.

Fluorescent Lights are good for raising herbs and other plants that do not need so much light. However, they are not suited for plants that are flowering because they do not put off sufficient light.

Compact fluorescents are smaller plus they are more productive than traditional kinds of fluorescent lighting that is why they can be utilized for all kinds of plants.

High-Intensity Discharge or HID bulbs are the best of all and most effective lights possible, but they are more expensive.

Have a look at our grow lights collection!


There are greenhouse designs that do not rely on heat or need heat. However, not all greenhouses are created that way. These season extension heaters can achieve some of the earth’s essential warmth, particularly in the evening, and prevent the chilling, and dehydrating impact of winter.

Electric heaters are the popular ones used, but you can also opt for propane or gas heaters. Control the temperature inside your greenhouse with these Greenhouse Heaters!

Always remember that planting seeds depend more on ground temperature than the air temperature. If your soil can be warmed sufficiently for the seeds to sprout, then they may be able to tolerate cooler air. You need to understand the temperature requirements of your plants and get a reliable thermometer.

A good heating system is a top priority for your winter greenhouse. While your plants need sufficient heat during the cold months, certain kinds of diseases would also grow along with the plants if left unchecked.

Is it your first winter with your greenhouse? Or are you looking for a greenhouse for winter gardening? Let us know in the comments!

Using your greenhouse in autumn

Don’t leave your greenhouse standing empty over autumn and winter. The protection it provides will not only help you to keep tender plants frost-free – it will also let you grow hardy crops, such as salads and herbs, all winter.


An unheated greenhouse can keep overnight temperatures as much as 5°C warmer than outside, which will keep plants frost-free in all but the worst of winters. It will also ensure plants stay dry, which greatly aids survival. A dry plant is much less likely to freeze than a damp one. It is often the combination of cold and wet that kills borderline-tender plants outside over winter.

Find out how to keep the heat in your greenhouse in winter.

The main consideration is to make sure your plants get plenty of light, as natural light levels are low in winter. Remove any shading material and clean the glass to maximise available light.

The following plants are all ideal for growing in a cold greenhouse through autumn and winter.

The protection the greenhouse provides will not only help you to keep tender plants frost-free – it will also let you grow hardy crops, such as salads and herbs, all winter.

Winter salads

Using your greenhouse in autumn – Mizuna leaves

Try hardy lettuces, such as ‘Salad Bowl’, as well as rocket, pak choi, mizuna, lamb’s lettuce and spinach. Sow in trays or pots of compost, then plant seedlings into large containers, border soil or this year’s old growing bags. Find out more about growing winter salad.

Hardy herbs

Using your greenhouse in autumn – Repotting chives

Pot up chives, parsley and mint in autumn and bring them into the greenhouse, where they’ll continue growing all winter. It’s worth planting up several pots of each, so you can harvest them in succession for a continuous supply. Watch our video guide to growing herbs in a greenhouse in winter.

Tender perennials

Using your greenhouse in autumn – pelargonium flowers

Many summer bedding plants can be overwintered in a cold greenhouse, including fuchsias, marguerites and pelargoniums. The extra protection provided will keep these plants alive. Water sparingly.


Using your greenhouse in autumn – rhubarb

Lift a rhubarb crown in autumn and leave it on the soil surface – it’s hardy enough to survive being frosted. Bring the crown into the greenhouse in late December and cover with a large tub to exclude light. Pick the stems when 30cm long.

Peaches and nectarines

Using your greenhouse in autumn – peaches

Prone to peach leaf curl fungus, the foliage of both plants can be kept disease-free if planted in the border of a cold greenhouse in autumn, or grown in pots that are kept under cover between October and late March. Read our peaches and nectarines Grow Guide.


Using your greenhouse in autumn – lewisia flowers

Although most are hardy, alpines benefit from protection during wet weather, as this spoils the flowers and encourages rotting. Bring plants indoors over winter, then move them outside again once the flowers fade. Discover 10 alpines to grow.

Spring bulbs

Using your greenhouse in autumn – tulip bulbs Advertisement

Pot up tulips, daffodils and hyacinths in autumn and stand them outside for six weeks. Then bring into the greenhouse to encourage early blooms. When buds appear, take the pots into the house and enjoy the display. Discover nine spring bulbs to force in autumn.

The joy of winter gardening in the best year round greenhouse for cold, wind and snow

Winter gardening in your Growing Dome greenhouse is an amazing experience. Walking in your dome from the lifeless vegetation outside into a thriving garden is both enlightening and empowering.

The ability to grow fresh produce year round is a major benefit of the Growing Dome geodesic greenhouse kit. Furthermore, winter greenhouse gardening is possible without supplemental heat.

Winter greenhouse gardening in a Growing Dome

The Growing Dome Greenhouse is designed as a self-sufficient, net zero energy structure.

It is capable of growing food year round in most climates of the United States, without additional heat, even in the heart of winter.

Through the design of its systems, the Growing Dome Greenhouse comes equipped with its own internal heaters…

…the above ground pond and the solar powered central air system.

Furthermore, given the amount of insulation, and the inherent energy efficiency of its geodesic shape, it requires a third less energy than a traditional greenhouse. It can withstand winter temperatures down to zero outside, while not freezing inside.

With over 30 years of experience, we know that the design is sound and effective, which means that we have confidence that you can grow frost hearty plants in the winter without additional heating of your Growing Dome Greenhouse.

Fresh flowers and produce year-round

There are still a few reasons why you might want to heat your Growing Dome in the winter.

  • You are growing tropical plants, tomatoes or plants that like warmer temperatures year round
  • You live in a zone that gets <50% sunlight per day in the winter
  • Temperatures consistently get into the single digits or below at night in the winter

This article shows what plants thrive in the winter without supplemental heat, but we will also recommend when and what type of heaters you should use in your Growing Dome Greenhouse.

Winter Greenhouse Gardening: Frost Hardy Crops

The following list of edible and/or medicinal crops have been grown successfully through the winter months in our Growing Dome greenhouse kits without supplemental heat. The best time to start your winter crops is in late August, or early September, but we have had success with fast growing crops as late as October. Most of the perennial crops, like Oregano, will live happily in the geodesic greenhouse year-round, but it is best to start them in the spring so they have plenty of roots and shoots before winter. The following frost hardy crops are categorized by their scientific family names. Focusing on edible herbs, leafy greens, and root vegetables, this list is by no means exhaustive. Fruiting crops like tomatoes or cucumbers are best started in late winter or early spring and grown all summer long. Tomatoes can make it through the winter and live for years if properly maintained and fed, but it takes extra effort, time, and energy, depending on your climate.

Amaranthaceae Family

Swiss Chard

Amaryllidaceae Family (aka. Amaryllis Family)

Garlic Chives
Green or Bunching Onions

Apiaceae or Umbelliferae Family (aka. Carrot, Celery, or Parsley Family)

Cilantro (aka. Coriander)

Asteraceae Family (aka. Daisy Family)

Chicory (Endive)

Boraginaceae Family


Brassicaceae Family (aka. Cabbage, Cruciferous, or Mustard Family)

Bok Choy
Brussels Sprouts

Fabaceae Family (aka. Bean, Legume, or Pea Family)

Sweet Pea or Sugar Snap Pea
Snow Pea

Lamiaceae or Labiatae Family (aka. Mint, Sage, or Deadnettle Family)

Bee Balm
Catnip or Catmint
Lemon Balm
Savory (winter)

Tropaeolaceae Family (aka. Nasturtium Family)


Grow frost hardy plants in the winter without additional heating

Heating Your Growing Dome In Winter Falls Into Three Main Levels Of Heating

First Level: No heating.

Second Level: Heating if the temperature gets into the single digits.

Third Level: Never letting the Growing Dome freeze.

Growing Dome Heat Loss Calculation Spread Sheet

Calculate exactly how much heat is required to reach a desired temperature inside your Growing Dome

No Heating

I have a number of friends here in Pagosa Springs, Colorado, who have chosen not to heat their Growing Dome greenhouses.

I personally have only heated my 22′ Growing Dome for one week in 15 years. That was after a week of no sun, followed by temperatures in the -20s!

A little ice forming on the tank inspired me to heat it.

However, I have grown many of the above-mentioned crops successfully.

Here is a shot of our 15′ Growing Dome, we are not heating it, and you can see that these frost hardy plants are doing great.

Heating When Temperatures Drop Into Single Digits

At Growing Spaces® we tend to heat our Growing Domes when the temperature dips into the single digits…

…because we want to encourage growth throughout the winter, maintain winter produce for our staff, and present an inspiring environment for our customers to see.

To this end, for our smaller Growing Dome greenhouses, we use a Mr. Heater in the winter.

It has three settings from 9000 BTU to 14,000 BTU which keeps smaller domes from freezing on those cold nights.

The disadvantage is that you have to light the heater at night and turn it off the next morning.

Never Letting The Growing Dome Freeze

A lot of people have frost sensitive plants including citrus and subtropical varieties of shrubs.

In this case, the heater we recommend is called a Southern Burner.

The beauty of this heater is that it is controlled by a thermostat so you can set the minimum temperature that you want the dome to go down to.

The Southern Burner heater gives out 25,000 BTUs which is enough to heat a 33′ Growing Dome greenhouse very adequately.

If you use a heater of this kind, there will be more condensation on the polycarbonate, which then drips down inside.

Some people have thought their dome was leaking, but this is usually not the case.

Here is another article on Heating the Growing Dome during the winter months, and a post written by a customer on Heating, Building, & Enjoying the Growing Dome.

Watch the winter greenhouse gardening video below to see the different types of heaters and what happens to the plants if they freeze.


Udgar Parsons

Winter Gardening in a Growing Dome greenhouse: No Heat Required

Please contact us if you’d like to get more information on Growing Domes. Or to receive more informative gardening and Growing Dome articles, please sign up for our monthly Newsletter “The Happy Grower“

A greenhouse is a great asset when growing vegetables in your garden, extending your growing season and even providing you with fresh vegetables through the winter and early spring. Successful greenhouse vegetable gardening requires the right environment, taking into consideration heat (in cooler months), cooling (in warm months), ventilation, air circulation, shading, humidity and lighting.

Starting seeds: Seed starting for a vegetable garden is a common use for a greenhouse. Greenhouse vegetable gardening gives an early start to your garden. You need containers, soil, fertilizer, water, and in cool, northern areas, heat and light. Propagation mats under seed flats helps germination by warming the soil. Seeds can also be planted directly into a soil bench warmed by a soil cable.

Heating: Heat for greenhouse vegetable gardening can be provided with electric, natural gas or LP gas heaters. Electric heaters are simple. 240 volt heaters are generally more efficient than 120 volt, but a 120 volt heater is generally adequate for heating a small greenhouse when controlled by a separate heavy-duty thermostat. Natural gas and LP heaters should be properly vented, providing fresh air for combustion and exhausting fumes, and equipped with a good thermostat. Less common methods include in-the-floor radiant heating or an extension of a forced-air home heating system to an attached greenhouse.

Lighting: Light is key to successful greenhouse vegetable gardening. If the natural light in your greenhouse is low (a common issue in winter), supplemental lighting helps keep plants from getting spindly. A fluorescent shop light hung about 4 inches above your plants may be enough. However, the new High Output Fluorescent lamps, High Pressure Sodium or Metal Halide lights provide strong, full spectrum light and can often cover a larger area than ordinary fluorescent. High output fluorescent lamps are energy efficient as well.

Vegetables to grow in the winter greenhouse: Vegetables best for greenhouse vegetable gardening in the winter include lettuce, spinach, radishes, tomatoes, peppers, and cucumbers. However, what you are actually able to successfully grow depends on the night time temperatures you decide to keep. A cool greenhouse, with night time temperatures of 40-45°F, works for lettuce, spinach and radishes. Peppers, tomatoes, and cucumbers need warmer temperatures at night, around 65°F, especially when fruit is growing.

Pollination: Pollination can be an issue for greenhouse vegetable gardening. Standard cucumbers will need hand pollination, taking the male blossom and gently rubbing the female blossom center. Tomatoes and peppers are self-pollinating but the blossoms should be gently shaken or vibrated on a regular basis. Circulation fans are great for that. Some seed catalogs offer varieties of seeds that are appropriate for greenhouse production, often due to their method of pollination. Johnny’s Selected Seeds is one seed catalog that clearly labels greenhouse appropriate varieties.

Watering: Water is needed, but the amount and frequency varies with temperatures, day length, plant size and soil mix. It is recommended that the plants be thoroughly soaked at every watering. In January, watering may be needed every 10 to 14 days. As the days get warmer, the frequency should be increased. Seedlings being warmed by a heat mat will dry out more quickly. When watering, avoid splashing foliage to prevent spreading diseases.

Ventilation: Greenhouse vegetable gardening in the winter can have an issue with the growth of mold and mildew. Do not over water. Control humidity with proper ventilation and air circulation. We recommend an oscillating fan running 24/7 all year long. In the warmer months, the most gentle form of ventilation is through natural convection with base wall vents or jalousie (louvered) windows pulling cool air in down low, with roof vents allowing hot air out through the roof.

Cooling: Positive cooling is usually not needed for greenhouse vegetable gardening as long as adequate humidity and shading is provided on hot days. If positive cooling is needed we recommend evaporative air coolers which humidify as they cool. Air conditioners are not good for plants since they remove moisture from the air.

Nothing should be growing this winter day on these frozen, rolling hills.

Yet here are green vegetables, kale and lettuce, growing in near-90 degree temperatures. They’re thriving in a specialized “deep winter” greenhouse, letting farmers Tom Prieve and Sue Wika grow fresh vegetables year round — without a crushing electric bill.

Their plants survive largely on natural winter light. Fans force rising heat down into a rock storage area, part of a passive solar heating system that captures the day’s warmth and releases it at night. On cold nights, a gas heater kicks in to help keep the temperature at 42 degrees. There are no banks of artificial lights.

It’s a different kind of greenhouse, mixing technology and old school ingenuity to create an energy efficient winter farm. University of Minnesota researchers say the idea is starting to take off. About two dozen deep winter greenhouses can be found now in Minnesota. Many more are in the planning stages. A deep winter growing association will soon give winter gardeners a place to share what they’re learning.

A small loft offers a bird’s-eye view of the deep-winter greenhouse at Paradox Farm in southern Otter Tail County not far from Lake Christina on Tuesday, Jan. 28, 2014. Temperatures inside the greenhouse vary by elevation with this thermometer indicating around 85 degrees near the peak. Paradox Farm is owned by Sue Wika and Tom Prieve. (Ann Arbor Miller for MPR) Ann Arbor Miller/For MPR News

The small operations can be put up and run without spending a lot of money. Wika and Prieve’s $5,000 winter greenhouse near Ashby is built like a lean-to against the south wall of the barn. Clear plastic panels cover the south wall, which is slanted at a 60 degree angle to best catch the midwinter sunlight. Next year a wood stove will help fight the overnight chill.

“I want people to know that this is a definite reality for people in northern climates,” Wika says. “They can have greens in the depths of winter.”

This is the second winter green plants have filled her greenhouse. Wika, the chief gardener, keeps careful records on everything growing. She says she’s still learning. What plants are best suited to winter production? What soil works best? What’s the most efficient way to heat the greenhouse at night? Who has the best ideas for affordable construction?

Dozens of 3-foot-long pieces of plastic roof gutter filled with soil hang from the ceiling. Rows of them are suspended from just above the floor to head high. Thick green vegetation spills over the sides.

Sue Wika’s enthusiasm for sustainable food production including a deep-winter greenhouse is evident when she talks about Paradox Farm and its farming practices. Building and using a deep-winter greenhouse, which combines passive solar energy with underground heat storage, is both durable and doable, says Wika. Ann Arbor Miller/For MPR News

On the floor are plastic bags of soil with holes cut in them. Chinese cabbage, turnips, radishes and beets sprout from the bags. The heated rocks under the floor keep them warm.

“Today we’ll harvest some red Russian kale and we’ll also harvest some of this komatsuna which is another really fast growing and productive Asian green,” says Wika, who praises the Asian greens as the “the real star in these deep winter greenhouses.”

There are also trays of barley, looking like squares of lush green grass – a treat for the goats and cows the couple milk as part of their sustainable farming effort.

“When it comes to feeding time you just simply peel it out of there and chunk it up and they gobble it down,” says Prieve, who trained as a large animal veterinarian. “It’s candy, they look for it first thing when they come in and it’s a more healthy form of energy than the straight grain.”

In about a month, the greenhouse will be filled with young tomatoes and other plants getting a head start on the outdoor gardening season. In summer, Wika uses the greenhouse as a giant dehydrator to make sun-dried tomatoes.

Rain gutters in assorted colors and sizes provide growing space for a variety greens for both human and animal consumption. Leafy vegetables like chard, red Russian kale, Chinese cabbage and komatsuna are among those being grown in a deep-winter greenhouse at Paradox Farm. Ann Arbor Miller/For MPR News

Wika and Prieve eat fresh greens every day and they sell or trade produce to six families in the area.

There are a lot of varieties that do very well in the winter with little care. Still, Wika spends about eight hours a week planting, watering and harvesting.

“I’m in here more time than I’m working,” says Wika, who holds a doctorate in sociology. “I always spend a lot of time just enjoying the sun and temperature. A lot of it is leisure and therapeutic.”

The plants will keep growing. Wika expects another harvest in three weeks. “They have amazing ability for recharging,” she says. “Some you might only get two harvests from, but there are some of these greens I might get four harvests from. They can be very productive.”

Wika places a tray of kale on a bench and starts trimming the thick bushy plants with a sharp knife, dropping the greens into a plastic tub. As she’s working, she sees Buddy Kasper peering into the greenhouse through fogged-over sunglasses. The 69-year-old drives 30 miles each week from Fergus Falls to get his fix of winter greens.

“You don’t even worry about salad dressing or anything. You reach in and grab a handful and stuff ’em in your mouth,” he says. “It’s just all of these different flavors come together at once. It’s all you need in the dead of winter.”

Gallery Fullscreen SlidePrevious Slide 9 of 9 A deep-winter greenhouse was added on to an existing building at Paradox Farm in southern Otter Tail County. The structure’s exterior walls are wood and polycarbonate. The farm sits on 160 acres and is owned by Tom Prieve, pictured, and Sue Wika.Ann Arbor Miller/For MPR News 1 of 9 Icicles collect on the exterior of a deep-winter greenhouse comprised of polycarbonate and other materials at Paradox Farm in southern Otter Tail County on Tuesday, Jan. 28, 2014. Temperatures outside hovered around -15 degrees compared to 80 degrees inside the greenhouse.Ann Arbor Miller/For MPR News 2 of 9 A small loft offers a bird’s-eye view of the deep-winter greenhouse at Paradox Farm in southern Otter Tail County not far from Lake Christina on Tuesday, Jan. 28, 2014. Temperatures inside the greenhouse vary by elevation with this thermometer indicating around 85 degrees near the peak.Ann Arbor Miller / For MPR News

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