Seed starting calendar zone 5

Zone 5 Seed Starting: When To Start Seeds In Zone 5 Gardens

The imminent arrival of spring heralds the planting season. Starting your tender vegetables at the correct time will ensure healthy plants that can produce bumper crops. You need to know the best time for planting seeds in zone 5 to avoid killing freezes and get the best yields. The key is knowing the date of your last frost and using tricks like raised beds and cold frames to get a jump start on that garden. Read on to find out when to start seeds in zone 5.

Seed Planting Times for Zone 5

Zone 5 has a shorter growing season than warmer climes. That doesn’t mean you can’t get loads of produce, but it does mean you need to check your seed packets and pay attention to the “days to maturity” portion of the instructions. This will tell you how long your seeds will take from planting to harvest. Some vegetables are cool season crops and can be started even when outdoor temperatures are still cool while others such as melons, tomatoesand eggplantrequire warm soil to germinate and bright, sunny, warm conditions.

Timing your planting correctly is crucial to successful harvests, but when to start seeds in zone 5? The first official frost free date is May 30 while the first chance of a freeze is October 30. That means you need to choose plants that will mature before late October and get them started as soon as possible to extend your growing season.

Some gardeners in cooler regions opt to use transplants that they set out in late May, while others grow in greenhouses to get a jump start. If that option is not available to you, or you prefer to start seeds in the ground, May 30 is your date for zone 5 seed starting.

May 30 is a ball park date. If your area is exposed, high in the mountains or tends to get frost pockets late into the season, you will need to adjust your planting time. Seed packets contain a lot of helpful information, including regional planting times. Usually, this is displayed on a map which is color coded to correspond to specific dates. These are the seed company’s suggested planting times and it will vary dependent upon the type of vegetable or fruit. These suggestions will give you a better idea of seed planting times for zone 5.

Properly preparing soil with plenty of organic material, assuring percolation and removing impediments to tiny seedlings is equally important.

Tips on Zone 5 Vegetable Planting

Cool season vegetables like brassicas, beets, spring onions and others can usually be planted as soon as soil is workable. That means they may experience a late season freeze. To protect seedlings, erect a hoop house to keep ice crystals off the plants. This will slightly raise the temperature inside and prevent severe damage to young vegetables.

Due to the late start date for planting seeds in zone 5, some produce that needs a longer growing season should be started indoors and transplanted out at the end of May. These are tender plants and cannot get the growing time they need by starting them earlier outdoors because they will fail to germinate. Starting seeds in flats indoors can give you decent sized plants that are ready for the appropriate outdoor planting time.

For additional information on when and what vegetables to plant in zone 5 regions, check with your local extension office for assistance.

Snow on the ground is not a good reason to procrastinate starting seeds. Starting seeds indoors in late February and early March ensures seedlings are strong enough to move outdoors after the last frost. By April the hardened seedlings will be raring to transplant into your garden or field.

Why start my own seeds?

Most nurseries and garden centers only offer five or six popular and proven varieties of tomatoes. If you typically buy your seedlings from a store, you may not know that there are over 2,000 tomato cultivars to choose from. My personal favorites, Amish Paste and Hillbilly, are regional heirloom tomato varieties not stocked in traditional stores. Starting my own seeds allows me to grow weird, wild and wonderful vegetables that customers love!


How do I grow vegetables indoors over winter?

Infographic: Starting seeds indoors

How to understand USDA hardiness zones

Starting seeds is much less expensive than buying seedlings. Small farmers and market gardeners find starting their own seedlings is critical to produce profits. For example, a single Cayenne pepper seedling costs $3 at the store. A packet of 25 seeds costs about the same. A 90% germination rate will produce roughly 23 home grown pepper seedlings for the same price as one store-bought pepper seedling.

Starting your own seeds allows you to choose varieties well-suited to your growing region. Last summer many of my neighbors complained when their robust tomato plants suddenly began to die from the bottom up. All of their plants were grown from store-bought seedlings. I had no problems with the tomato plants I started from seed. It’s possible my heirloom tomatoes were better-adapted to our area. Plants historically grown in a region evolve to deal with that region’s climate conditions, diseases and pests.

Grow plants appropriate to your region:

Where is the best place to buy seeds?

When I moved north of the Mason-Dixon Line, I had to give up my southern seed sources and find seeds better suited for my growing region. Seed that is grown, tested, and produced in a specific area has best germination and yield results when grown in similar conditions. Test garden and source location information is typically found within the first few pages of a seed catalog.

A seed’s rate of germination declines every year after it is packaged. Reputable seed companies only ship seed packaged for the year you purchase it. If you buy seed from a traditional store, check the seed packet for a current date.

Seeds to start indoors: Broccoli
Brussels sprouts

Ten steps to start seeds:

  1. Read seed packet for planting information, paying close attention to depth.
  2. Fill seed starting containers ¾ full with potting medium.
  3. Sow seeds at appropriate depth. Cover loosely with soil.
  4. Moisten with water. Keep soil damp and warm, 80 degrees F, for good germination in 5-10 days.
  5. After germination keep soil moist but not damp. Peat pots have a tendency to run dry. Plastic containers tend to retain water. If you see mold on container or soil surface, your soil is too wet. Water less and add a fan to increase air circulation.
  6. After germination reduce temperature to 70 degrees F.
  7. Give seedlings between 14-18 hours of light a day.
  8. Thin seedlings as required.
  9. Use diluted fertilizer or compost to feed seedlings as required.
  10. After the last frost, gradually harden off seedlings outdoors. Start by moving the seedlings outside on warm sunny days and gradually increase exposure. The seedlings will be ready to transplant in the garden after 2 weeks hardening.

A final note about starting seeds indoors: Garden supply centers sell mini greenhouses, hoop houses and cold frames for starting seeds. But remember that without supplemental heat, these outdoor structures are not warm enough to start seeds in early spring. In USDA hardiness zones 5 and below you will have to add an additional layer of plastic to the outside of your unheated structure, or use heated mats and warm rain barrels to increase the temperature inside.

Additionally, you can utilize unheated space in outdoor structures to harden off seedlings. If you live in zone 5 or lower, I recommend starting seeds indoors. Simple and effective homemade grow system plans are free to download online.

I use homemade indoor grow systems with adjustable fluorescent bulbs to start my seeds. My design is based on free plans from Cornell University. If you have strong sunlight from south facing windows, a couple of 2×8’s laid across coffee tables may be all you need to successfully start seeds.

Get a head start on the growing season by starting seeds indoors now. Tiny sprouts peeking through the soil surface will help make these last few weeks of winter bearable.


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Seed Starting Timetable for Tomatoes

This seed starting timetable allows 8 weeks for seeds to germinate, grow at least two sets of leaves (or more), reach transplant size, and harden off before setting in the garden.

Here are some general rules to follow in North America (according to hardiness zones outlined by the United States Department of Agriculture) about when to start your tomato seeds.

Zones 9 & 10: Start seeds indoors in early to mid January
Zone 8: Start seeds indoors in early February
Zone 7: Start seeds indoors in mid February
Zone 6: Start seeds indoors in late February
Zone 5: Start seeds indoors in early March
Zones 1-4: Start seeds indoors in mid to late March


Before you leave …

Get your free copy of “10 Must-Know Tomato Growing Tips.” This 20-page guide is filled with tips you need to know to have a successful tomato crop, whether you’re a beginning or experienced gardener.

What’s a “plant hardiness zone”?

The USDA Hardiness Zone Map divides North America into 11 separate zones, called “plant hardiness zones.”

Each zone is 10°F warmer (or colder) in an average winter than the adjacent zone. The map was developed to provide climate information important to horticulture.

Most gardeners in North America rely on the USDA Hardiness Zone Map as they plan gardens and choose plants.

Gardeners in other parts of the world use plant hardiness zone maps that follow the USDA model but are modified for their particular climate. For example, Africa’s map is divided into 13 hardiness zones. Australia’s temperatures are mild across the continent; its hardiness zone map is divided into just 5 zones and noted in metric units.

Tomato seed starting timetable at a glance

When to sow tomato seeds indoors

6-8 weeks before last freeze date

When to transplant tomato seedlings to the garden

1 to 2 weeks after last spring frost

When to sow tomato seeds outdoors

After last spring frost (if your season is long)

Other tomato seed sowing details

Germination time: 6-14 days, depending on variety
Germination temperature: 70-85º F
Sowing depth: 1/4 inch
Days to maturity: 53-90 days from transplant, depending on variety

See more tomato growing tips on our Pinterest board.
More on starting tomato seeds
When to start tomato seeds in your area …
Growing tomatoes from seeds: what you need to know …
Seed starting containers to use when you start tomatoes …
Compare seed starting kits for growing tomatoes …
What potting mix to use when growing tomatoes from seeds …
Review: Pro-Mix Seed Starting Mix for growing tomatoes from seeds …
Learn what tomato seedlings need after they germinate …

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Figuring out when to start seeds indoors is difficult, especially when you’re new to seed starting. In this post I will show you exactly how to figure out when to start planting seeds, and help you create your own personal seed planting schedule.

When should you start seeds indoors? This is one of the most common questions I get from new gardeners.

There are lots of different seed planting charts out there, and they can be helpful to use as a guide. But, there are so many factors involved in the timing of starting seeds that it’s best to create your own personal seed starting timetable.

Why Do We Need A Seed Starting Timetable?

Timing is very important when it comes to starting seeds indoors under lights. That’s because if you start your seeds too early, you could end up with weak, leggy seedlings that won’t survive the transition to the garden in the spring.

But if you start your seeds too late, the seedlings won’t be mature enough for transplanting into the garden by spring.

It takes a little practice, but don’t worry – in time you will be able to create your own seed planting schedule so you know exactly when to start your favorite seeds. Let’s walk through the steps together…

When should you start seeds indoors

Figuring Out When To Start Seeds Indoors

The biggest problem with figuring out what to plant when is that every seed is different.

Some seeds are fast growers, and it will only take a few weeks for the seedlings to grow large enough to be transplanted into the garden. But other seeds are very slow to germinate, and it takes much longer for the seedlings to grow.

Plus, every growing zone has different seed starting dates. So there is no such thing as a “one size fits all” seed starting chart.

So how can you figure out the best planting dates for YOUR seeds?

Finding Your Best Planting Dates For Seeds

Since every seed is different, and some have special planting instructions, we need to rely on the seed packets for help.

Unfortunately, many seed companies give us very vague planting details (or no instructions at all), which is super annoying.

But don’t worry, I’ve got you covered. If you’re just starting out, you can follow these simple guidelines to figure out a basic seed starting timetable…

Figuring out when to start seeds indoors

Step 1: Find the seed starting dates on the seed packet – First, read the instructions on each of your seed packets to find the recommended planting dates for each type of seed.

Most seed packets will give you recommendations for when to start seeds indoors.

Finding the best planting dates for seeds

Step 2: Sort your seed packets by best planting dates – Take all of the seed packets you plan to start indoors and sort them by the recommended seed starting dates shown on the packet.

Generally, it will be something like “4 to 6 weeks before average last frost”, or “6 to 8 weeks…” etc.

Sorting seed packets by best planting days

Once you have all of your seed packets sorted into piles, store them this way so when it’s time for planting seeds, you know exactly which ones to start at the same time.

But wait… what if your seed packets don’t have any recommended planting dates on them?

General Guideline For When To Plant Garden Seeds Indoors

Unfortunately, not all companies include seed starting dates on the packets for you (I guess they like to keep us guessing).

So if your seed packet is less than helpful, and you can’t find recommended seed planting dates online, then you should plan to start those seeds indoors 6 to 8 weeks before the average last frost date in your growing zone.

The average last frost date is different for each growing zone, and it’s important to know what yours is. If you don’t know the average last frost date in your growing zone, visit your local garden center and ask them, or look it up online.

For example, our average last frost date here in growing zone 4b (Minneapolis, MN) is May 15th.

So, I would count backwards 6 to 8 weeks (which would be March 20th – April 3rd), and that’s when I would start planting seeds indoors.

Related Post: 17 Easiest Seeds To Start Indoors

Starting seeds indoors based on a seed starting timetable

How To Create Your Own Seed Planting Schedule

Once you figure out when to start each type of seed indoors, then you can work to create your own seed planting schedule to make your life easier year after year.

When the time comes for you to start planting seeds indoors, keep track of the dates you planted each type of seed, and make a note of when the seeds started to grow.

You should also keep a record of how well each of the seeds grew. Did the seedlings grow long and leggy before you could move them outside? Did they outgrow their containers? Or maybe they were too small to plant into the garden in the spring.

Write it all down.

Knowing when to start seedlings indoors is super important

This will give you a good start on your custom seed planting schedule. Then next year you can make the necessary adjustments.

Any seedlings that became too large or leggy before you were able to move them outside should be started indoors a week or two later next year.

On the other hand, seedlings that were too small to transplant into the garden should be started a couple weeks earlier next year.

How to create your own seed planting schedule

Once you get the hang of knowing when to plant garden seeds indoors, you will have your own custom seed planting schedule to go by year after year.

Also, you’ll begin to see patterns for certain types of vegetable and flower seeds, and know which seeds to plant at the same time – and this will make starting seeds much easier for you.

Related Post: Tips For Starting Seeds Indoors For Beginners

How do you know when to start seeds indoors

There are tons of garden seed planting guides online that can be helpful to give you an idea of what to plant when. But there’s no such thing as a “one size fits all” indoor seed starting chart!

It’s best to create your own custom seed starting timetable that you can use year after year. If you want to learn more about how to start you seeds indoors, then my Starting Seeds Indoors eBook would be perfect! It’s a quick-start guide that will have you up and running in no time.

If you need more, and you want to learn everything you need to grow all of your own seeds without wasting time, money and frustration, then The Seed Starting Course is exactly what you need! You will learn everything from exactly how and when to plant your seeds and caring for your seedlings, to saving money on equipment and supplies, learning exactly how and when to plant your seedlings into your garden so they will thrive, and a creating a customized seed starting plan to save you time and money year after year, so you’ll be all set for success. Enroll in the course today!

More Information About Growing Seeds

  • Seed Starting Equipment and Supplies
  • How To Test The Viability Of Seeds With An Easy Seed Germination Test
  • Seed Starting Peat Pellets Vs. Soil: Which Should You Use And Why?
  • How To Make Your Own DIY Seed Starting Mix (with recipe!)

Have you created your own seed planting schedule so you know when to start seeds indoors? Share your experiences and tips in the comments section below.

A Zone 5/6 Seed Starting Schedule can start as early as January with lettuce & other greens. March & April are the months for starting most of your crops!

First off let’s start out with me giving you an important link. This post is meant for those of you living in Zones 5 and 6. If you don’t know your garden zone go to this post to find out!

Today’s post is by request! A Zone 5/6 Seed Starting Schedule. One of my readers who lives fairly close by in our “neck of the woods” as she put it, asked for a breakdown of when I get seeds started indoors.

Please keep a couple of things in mind:

First, this schedule would be for someone who lives in a warm zone 5 or zone 6 (we live in zone 6).

Second, we have cold frames and hoop houses to offer protection to some of our earliest spring and latest fall plantings so if you don’t have a way to protect your seedlings you will want to skip the really early plantings of lettuce.

A couple of other guidelines for this Zone 5/6 Seed Starting Schedule. I try to time all my seedlings so that they spend no more than 6 or 7 weeks indoors. Usually, 6 weeks under the lights and another week outdoors hardening off, any more time than that and you will stunt the plants because they will become root-bound in the pots. We love lettuce for our salads. Every year I set out with a plan to plant about 8 lettuce plants every 3 weeks. That’s always the plan, not always the reality. When we do hit that goal it gives us a couple of heads of lettuce to eat per week. If you don’t like lettuce that much adjust your plan accordingly.

Here’s our zone 5/6 seed starting schedule

So there it is. Of course, this is based on my experience and what has worked best for our garden, I’m sure some of my gardening friends may have different dates. I’ve been growing my own vegetable seedlings for years, my flower experience is much more limited so I won’t swear by those dates (yet). This year we really want to add a lot of color to our yard so we will be growing a lot more of our own flower seedlings, so I should have a lot more experience next year!!

A few other comments

1. If you don’t have a cold frame or hoop house (why don’t you!!) then you really wouldn’t need to worry about getting anything started until mid-February.

2. I don’t always get melons, cucumbers, and squash planted indoors. If you do try them you should only plant them about 3 weeks early. You want your seedlings to be very small with only 3 or 4 true leaves, anything larger won’t transplant well. But in our area, all of those plants do well when seeded directly in mid-May so it’s not the end of the world if I don’t get seedlings.

3. Lots of people question why I start all my lettuce indoors when lettuce does so well when sown directly. It’s really just my preference, I get a much better “finished product” when I start them indoors. Also starting them indoors allows me 6 more weeks of growing something else outside in the garden while the lettuce is getting started indoors.

As you can see from this zone 5/6 seed starting schedule, our seed starting operation is pretty busy from January until October, but growing my own seedlings saves us a ton of money and time. I hope this helps!!

Would you like to learn more about seed starting? Well, why not take our online video course.

Starting Plants Indoors From Seeds

Revised by David H. Trinklein
Division of Plant Sciences

Many flowers and vegetables may be started from seeds indoors. Vigorous plants started indoors flower sooner and produce an earlier harvest than plants started outdoors. Seeds of certain species, however, are best sown directly outdoors when weather conditions permit and are actually delayed by transplanting.

Growing plants from seeds can be a rewarding hobby and also allows home gardeners to grow varieties that may not be available from local plant outlets.

Seeding date

The proper time for sowing seeds indoors depends on the amount of time required to develop a healthy transplant of appropriate size to be moved outdoors. This period may range from 3 to 15 weeks, depending on species and the cultural conditions in the home (see Tables 1 and 2).

Additionally, the date at which a species may be transplanted into the garden must be considered when establishing a seeding date. Cold-tolerant plants such as pansy and cabbage often can be set out in late March or early April and must be seeded relatively early in the year. Heat-loving plants such as vinca and watermelon should not be set out until the weather has warmed, usually in late May, and should be started later.

Table 1
Guide to sowing common annual flower seeds in the home.

Flower type Seeding date1 Germination time Growing temperature Crop time
Ageratum Early March 5 to 8 days 60 to 65 degrees F 10 to 11 weeks Needs light to germinate.
Alyssum, sweet Late March 4 to 8 days 50 to 55 degrees F 8 to 9 weeks Needs light to germinate.
Aster Early April 8 to 10 days 60 to 62 degrees F 7 to 8 weeks
Begonia, fibrous Early to mid-January 10 to 12 days 60 degrees F 16 weeks Needs light to germinate.
Celosia Early April 6 to 10 days 65 to 68 degrees F 10 to 12 weeks Don’t grow cool.
Cleome Early to mid-April 10 to 12 days 70 to 75 degrees F 7 to 9 weeks Transplant before flowering.
Coleus Early March 8 to 10 days 65 to 75 degrees F 9 to 10 Needs light to germinate.
Cosmos Mid-April 5 days 65 degrees F 4 to 6 weeks
Dianthus Early March 5 to 7 days 50 to 55 degrees F 12 to 14 weeks Cover seeds lightly. Grow cool.
Dusty Miller Early March 10 to 15 days 60 to 65 degrees F 11 to 12 weeks Needs light to germinate.
Geranium, seed Early February 7 to 10 days 60 to 65 degrees F 13 to 15 weeks Best if grown in small pot.
Gomphrena Late March 10 to 14 days 68 degrees F 9 to 10 weeks Crop time for dwarf types.
Impatiens Mid-February 15 to 18 days 58 to 60 degrees F 10 to 11 weeks Cover seeds lightly.
Lobelia Early February 15 to 20 days 60 degrees F 11 to 12 weeks Needs light to germinate.
Marigold Early April 5 to 7 days 65 to 68 degrees F 8 to 12 weeks Tall types require more time.
Melampodium Early April 7 to 10 days 60 to 62 degrees F 7 to 8 weeks
Nicotiana Late March 10 to 15 days 60 to 62 degrees F 9 to 10 weeks Needs light to germinate.
Nierembergia Late March 10 to 15 days 60 to 62 degrees F 10 to 11 weeks Keep cool during germination.
Pansy/Viola Early to mid-January 6 to 10 days 50 to 55 degrees F 14 to 15 weeks Grow at cool temperatures.
Pepper, ornamental Early to mid-April 8 to 10 days 60 degrees F 11 to 14 weeks
Petunia Late February 6 to 12 days 55 to 60 degrees F 12 to 13 weeks Needs light to germinate.
Phlox, annual Late March 6 to 10 days 50 to 55 degrees F 10 to 11 weeks Direct seed into containers.
Portulaca Early April 6 to 10 days 65 degrees F 12 to 13 weeks Needs light to germinate.
Salvia Mid-March 12 to 15 days 60 degrees F 9 to 11 weeks Needs light to germinate.
Snapdragon Early March 7 to 12 days 45 to 50 degrees F 15 to 16 weeks Needs light. Grow cool.
Statice Mid-March 15 to 20 days 50 to 55 degrees F 8 to 10 weeks Grow at cool temperatures.
Stock Early February 10 to 14 days 50 to 55 degrees F 9 to 10 weeks Grow at cool temperatures.
Torenia Mid-February 10 to 15 days 55 to 60 degrees F 12 to 13 weeks Needs light to germinate.
Verbena Early March 12 to 20 days 55 to 60 degrees F 12 to 13 weeks Chill seeds before sowing.
Vinca Mid-March 10 to 15 days 65 to 68 degrees F 14 to 15 weeks Grow in warm temperatures.
Zinnia Mid-April 5 to 7 days 60 degrees F 8 to 9 weeks Direct seed into final container.
1Approximate seeding date listed is for mid-Missouri (Zone 5). In the Bootheel area (Zones 6/7), sow one to two weeks earlier. In northern Missouri, sow about one week later.

Table 2
Guide to sowing vegetable seeds in the home.

Vegetable type Seeding date1 Germination time Growing temperature Crop time
Broccoli Late February 5 to 10 days 50 to 60 degrees F 6 to 8 weeks Grow cool. Tolerates light frost after hardening.
Brussels sprouts Late February 5 to 10 days 50 to 60 degrees F 6 to 8 weeks Grow cool. Tolerates light frost after hardening.
Cabbage Late February 5 to 10 days 50 to 60 degrees F 6 to 8 weeks Grow cool. Tolerates light frost after hardening.
Cauliflower Late February 5 to 10 days 50 to 60 degrees F 6 to 8 weeks Grow cool. Tolerates light frost after hardening.
Cucumber Late April 7 days 60 to 62 degrees F 3 to 5 weeks Sow directly in pots. Keep warm at all times.
Eggplant Late March 7 to 14 days 62 to 65 degrees F 6 to 8 weeks Keep warm. Do not subject to frost.
Head lettuce Late February 5 to 10 days 50 to 60 degrees F 6 to 8 weeks Grow cool. Tolerates light frost after hardening.
Kale/Collards Late February 10 days 50 to 60 degrees F 6 to 8 weeks Grow cool. Tolerates light frost after hardening.
Muskmelon Late April 7 days 60 to 62 degrees F 3 to 5 weeks Sow directly in pots. Keep warm at all times.
Okra Late April 7 to 14 days 60 to 62 degrees F 4 to 6 weeks Sow directly in pots. Keep warm at all times.
Pepper Late March 7 to 14 days 62 to 65 degrees F 6 to 8 weeks for packs
8 to 10 weeks for pots
Keep warm. Do not subject to frost.
Pumpkin Late April 7 days 60 degrees F 4 to 6 weeks Sow directly in pots. Keep warm at all times.
Squash Late April 7 days 60 to 62 degrees F 3 to 5 weeks Sow directly in pots. Keep warm at all times.
Tomato Late March 7 to 14 days 62 to 65 degrees F 6 to 8 weeks for packs
8 to 10 for pots
Keep warm. Do not subject to frost.
Watermelon Late April 7 days 60 to 62 degrees F 3 to 5 weeks for pots Sow directly in pots. Keep warm at all times.

Selecting seeds for planting

Purity and trueness to type
Producing quality transplants starts with using good seeds. Seeds should have a high germination percentage and be genetically pure and free from seeds of weeds. For best results, obtain quality seeds from a reliable dealer.

Packages and storage
Seeds sold in packages should show species, variety, germination percentage and chemical seed treatments, if any. Seeds should be kept dry and cool to ensure good germination at planting. Laminated foil packets ensure dry storage. Paper packets are best kept in tightly closed jars containing a desiccant such as silica gel until seeds are planted.

Hybrid seeds
Most new vegetable and flower varieties are hybrids. Because they are more expensive to produce, hybrid seeds often cost more than seeds of nonhybrid varieties. However, hybrids usually have increased vigor, better uniformity, better production and sometimes specific disease resistance or other unique cultural characteristics.

Germination media

The medium used for starting seed should be loose, well-drained and fine-textured. Additionally it should not contain disease organisms or significant amounts or fertilizer. Prepared media possessing these traits are available commercially, or component materials can be purchased and mixed at home (Figure 1).

Figure 1
Soilless mixes that are porous and lightweight work well for seed germination.

Vermiculite is a naturally occurring, micaceous mineral that has been treated with heat, causing it to expand, or exfoliate. When used alone, it provides an environment conducive to good seed germination. It is clean and, if not contaminated during handling, will not need sterilization. If other seeding mixes are used, it is useful for covering seeds because it does not form a crust and allows easy emergence for the seedlings. Vermiculite is available in several size grades. For seeding, a fine grade is best.

Milled sphagnum moss
Sphagnum moss consists of the dried plants growing atop sphagnum peat bogs. When ground, this moss can be used for starting seeds and appears to have the ability to suppress certain seedling diseases. It should be well-moistened before use. Because it contains no fertility, prompt fertilization is essential after seeds have germinated.

Soilless mixes
Inert mixes containing no soil are available for starting seeds. These usually are composed of a combination of peat moss and vermiculite or perlite. They may be purchased ready-made or can be mixed at home. To prepare such a mix, use 4 quarts of vermiculite, 4 quarts of peat moss, 1 tablespoon of superphosphate and 2 tablespoons of pulverized limestone. These mixes have little fertility, so seedlings must be watered with a diluted fertilizer solution soon after they emerge.

Containers for sowing seeds

Containers for starting seeds should be sterile and free from harmful chemicals. Additionally, they should be sturdy and fit into the space available for growing plants in the home (Figure 2). The proper container helps get seedlings off to a good start and often saves work in later stages of transplant production.

Figure 2
A variety of containers appropriate for sowing seeds indoors are available.

Plastic trays, fiber trays or wooden flats
Plants that are easy to transplant may be seeded directly in trays or flats for later transplanting into individual packs or pots, or wider spacing in flats. Starting seeds in such containers saves space when compared with seeding directly into individual pots. However, when time is more important than space, direct seeding in pots may be preferred, especially for plants with large seeds, such as melons.

Plastic or clay pots
Both plastic and clay pots provide excellent growing conditions for transplants and can be sterilized and reused, if necessary. The transplant with its accompanying root ball must be removed from the pot carefully at planting time. Seeds may also be planted directly into the pots.

Peat pots
Biodegradable pots made from peat or paper waste fibers can be purchased individually or in strips or blocks. They are porous and provide excellent drainage and air circulation to the root zone. The entire pot can be planted, eliminating the problem of root disturbance at planting time.

Compressed peat pellets
Before hydration, expandable peat pellets are about the size of a silver dollar but somewhat thicker. When placed in water, they swell to form a cylindrical netlike container filled with peat moss, ready for seeding or transplanting. They may be planted directly into the garden. Use the pellets in trays so that they are easily watered and held upright.

Sterilizing containers

Sanitation is of utmost importance to help prevent plant diseases and thus produce quality transplants. Previously used or otherwise contaminated containers should be sterilized before use. Wash plastic or wooden containers thoroughly with soapy water to remove all debris. Then rinse containers by dipping them in a solution of one part chlorine bleach to nine parts water, and allow them to dry before filling with a germination medium.

Peat pots and peat pellets are considered biologically inert; however, be careful not to contaminate them through improper use or storage.

Steps in planting seeds

  • Moisten the germination medium to be used. Fill the container to within ¾ inch of the top with the medium. Make sure the container has adequate drainage. Use a clean, small board to level and gently firm the germination medium.
  • If seeding a tray or flat, use a ruler or large wooden plant label to make shallow rows 1 to 2 inches apart. When different seeds are used in the same tray, they are easier to keep track of if planted in rows. If only one variety of seed is used, it may be scattered or “broadcast” over the surface.
  • Sow the seeds uniformly and thinly in the rows. Many small, round seeds may be slowly dropped in the rows by tapping the package as it is held over the rows. Label each row promptly with plant type, variety and date of planting.
  • Plant large-seeded vegetables such as cucumber, cantaloupe and watermelon directly into containers such as peat pots. Other seeds may also be handled this way to save transplanting, but sowing is difficult with tiny seeds. Some small seeds are now available in “pelletized” form to make handling easier. Plant two seeds per pot and later thin to one plant. This saves later transplanting and results in less root damage at planting time.
  • Cover the seeds with dry vermiculite or milled sphagnum moss. The depth of covering depends on the size of the seeds. As a general rule, seeds other than especially fine seeds should be covered to a depth about two times their diameter. Most fine seeds, such as petunia and lettuce, need light to germinate and should not be covered.
  • Moisten the surface of the medium with a fine mist, or place the container in a pan of warm water to absorb it from the base. Don’t place the container in water that is deep enough to run over the top. Such flooding can mix seeds or cover them too deeply.
  • After hydrating the flats or containers, cover them with clear plastic. Large plastic bags work well. Because plastic retains moisture, no additional watering should be necessary until the seeds have germinated and the plastic has been removed.
  • Place seeded container in a warm location for germination. Generally, a range from 65 to 75 degrees F is best. A few plants such as larkspur, snapdragon, sweet pea, cabbage, broccoli and cauliflower are best started at about 55 degrees F. Do not place covered containers in direct sunlight.
  • Inspect daily for germination. Containers should be moved to bright light and the plastic cover should be removed as soon as germination is well under way. If not all seeds germinate at the same time, cut strips of plastic or cloth, and keep ungerminated rows covered until seedlings appear. Seeds are quickly killed if allowed to dry during germination. Watch closely for development of any disease and, if evident, take control measures promptly. After germination, plants listed as preferring cool temperatures should be placed in a cool location.

Seedling diseases

Newly emerged seedlings are delicate and quite vulnerable to a disease known as “damping off,” which is caused by the fungus Rhizoctonia solani (Figure 3). Symptoms include dark, sunken tissue at the base of the stem, where it enters the propagation medium. Toppling over at the ground line usually follows. Excess moisture, high temperature and poor light stimulate spread of the disease by weakening plants and making them more susceptible to it.

Strict sanitation is helpful in the prevention of damping off. For seeding, use only sterile containers and germination media free from pathogens. However, if damping off should occur, drench the entire medium with a fungicide registered for the control of Rhizoctonia. Prompt action is needed to prevent the disease from spreading to previously healthy seedlings.

Figure 3
Damping off (Rhizoctonia) is a fungal disease of seedlings that girdles the plant’s stem where it enters the growing medium, causing the plant to topple over.

Growing seedlings

After seeds have germinated, promptly give them the best possible growing conditions to ensure stocky, vigorous plants for outdoor planting. Cultural requirements must be controlled carefully to accomplish this.

Seedlings must receive bright light promptly after germination. Place them in a bright south-facing window if possible. If a large, bright window is not available, place the flats under fluorescent lamps. A fixture containing two 40-watt fluorescent lamps is adequate. A 50:50 combination of cool white and a fluorescent lamp specially designed for plant growing (plant light) is ideal. Place the seedlings about 6 inches from the lamps and keep lamps on for 14 to 16 hours each day. As seedlings grow, the lights may need to be raised to prevent leaf burn from seedlings touching the lamps.

Most annual plants and vegetables prefer night temperatures between 60 and 65 degrees F (Tables 1 and 2). Day temperatures may run about 10 degrees higher. If temperatures are warmer than this, plants become leggy. Cool-season vegetable crops and a few flowers prefer night temperatures no higher than 55 degrees F and day temperatures near 65 degrees. An unused bedroom, basement or sun porch is often a good location for these plants.

Good humidity and adequate water are necessary for producing good plants. A humidifier may be used to help increase relative humidity around the plants, or shallow pans of gravel filled with water may be placed as close to the growing area as possible. Adequate watering implies keeping growing medium moist at all times but never soggy. Allow some drying between watering, but don’t allow seedlings to wilt at any time. Never use water that has gone though a water softener to water plants, especially seedlings.

Seedlings will need some fertilization for best development. Because artificial, or soilless, mixes contain few, if any, nutrients, prompt and regular fertilization is necessary. Use a soluble houseplant fertilizer as sold in garden centers, nurseries or plant supply sections of department stores. Young, tender seedlings are easily damaged by too much fertilizer. Apply fertilizer at about half the recommended strength a few days after seedlings have germinated. After that, fertilize according to the recommendations on the fertilizer label. Water and fertilize carefully.

Transplanting seedlings

As soon as seedlings have developed at least one set of true leaves and are large enough to handle, they should be transplanted to individual pots or packs. Failure to transplant promptly results in crowded, spindly seedlings that may not be able to develop properly. Soilless potting mixes similar to germination media are preferred at this stage of transplant production.

To transplant, carefully dig up the small plants with a clean knife, spatula or plant label. Let the group of seedlings fall apart and pick out individual plants. Occasionally, if seedlings have been too close, they are difficult to separate. Gently ease them apart in small groups, which will make it easier to separate individual plants. Avoid tearing roots in the process. Handle small seedlings by their leaves; small, thin stems break easily.

After filling a container (pack or pot) with moist potting medium, poke a hole into it with a clean dibble (fingers also work well). Make the hole deep enough that the seedling can be put at the same depth it was growing in the seed flat. The size of the container usually is dictated by the size of the mature transplant. Small plants or slow growers are usually transplanted into bedding plant packs containing small individual cells. Rapid-growing, large seedlings should be planted individual pots. After planting, gently firm the medium and water. If seeds were sown in individual peat pots or pellets, thin them to one seedling at this time rather than transplanting them.

Keep newly transplanted seedlings shaded for a few days, or place them under fluorescent lights. Keep them away from heat sources or other conditions that would cause rapid water loss. Continue watering and fertilizing as was done in the seed flats.

Vegetables that are easily transplanted include broccoli, cabbage, brussels sprouts, lettuce and tomato. Those with slower root development include cauliflower, celery, eggplant, onion and pepper. Plants that do not transplant well and therefore are seeded in individual pots include cucumber, muskmelon, squash and watermelon.

Most flowers normally grown indoors transplant well, but a few are difficult to transplant. These include poppy, larkspur, lupine, sweet pea and cornflower. If started indoors, this group of plants should be directly seeded into small containers.

Moving plants outdoors

Plants that have been growing indoors under carefully controlled conditions are susceptible to transplant shock when moved to the garden. To prevent this from occurring, they should be “hardened” before planting outdoors.

The process of hardening involves subjecting transplants to cooler temperatures and giving them less fertilizer and water to “toughen” them. Hardening should be started about two weeks before planting in the garden. If possible, move plants to a shady, outdoor location with cooler temperatures. A coldframe is excellent for this purpose. When plants are first put outdoors, keep them in the shade, but gradually move them into sunlight for short periods each day, gradually increasing the length of exposure. Don’t put tender seedlings outdoors on windy days or when temperatures are below 45 degrees F. Reduce the frequency of watering to slow growth, but don’t allow plants to wilt. Even cold-hardy plants such as cabbage and pansy will be hurt if exposed to freezing temperatures before they have been hardened. After proper hardening, however, they can be planted outdoors, and light frosts will not damage them.

Planting into the garden
When plants have grown large enough to handle easily and hardening is complete, they may be planted into the garden when weather and soil conditions permit.

Carefully remove plants from the packs or pots in which they have been growing; take care to disturb the roots as little as possible. Dig a hole about twice as large as the root mass of the transplant. Set the transplant at about the same level it had been growing in the container. A few plants such as tomato and marigold are able to develop roots along the stem. If they have become leggy, they may be planted deeper than they were previously growing. Place soil loosely around the roots and apply about 1 cup of a starter solution. This solution is made by dissolving 1 tablespoon of high-phosphorus fertilizer, such as 9-45-15, in 1 gallon of water.

Transplants grown in peat pots or peat pellets can be planted with the pot or pellet intact. Breaking the base of the peat pot may help improve root penetration and drainage. Make sure the top edges of the pot are thoroughly covered with soil. Failure to do so exposes the pot edge, which acts as a wick and evaporates moisture from around the root ball. This delays root penetration or even causes the plant to dry up on hot, sunny days.

Transplant into the garden on cloudy days if possible. In warm, sunny weather, cover the new transplants with newspaper tents or some other type of shading for two or three days or until they are well established. Water plants as needed, making sure to apply water at the base of the plants until roots have had time to develop more fully.

Written by Ray R. Rothenberger, Department of Horticulture

Audio clips

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Audio clip 1
Clean containers are extremely important for good germination and prevention of disease. These petunia seedlings are heavily seeded and will need prompt transplanting soon.

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Audio clip 2
Watch for fungi growth and treat the spots promptly to prevent spread.

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Audio clip 3
These begonia seedlings have been transplanted into individual sections of a tray for development until they can be moved directly to the garden

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