- Protect Roses for the Winter
- Time to Winterize: Ready Roses for Winter
- Winter Hardiness
- Get Ready for Winter
- Winterizing Roses For Zones 7-13:
- Three Ways to Winterize Roses For Zones 1-6:
- How to Protect Your Roses in the Winter
- Cold Climates
- Extra-Cold Climates
- Hybrid Tea Rose
- Tree Rose
- Potted Roses
- October and November
- December and January
- Tips for Pruning Roses
- Pruning Tools for Rose Bushes
- Why Prune Roses?
- Rose Pruning Principles
- How to Prune Roses
- How to prune roses
- Spring cleanup
- How to deadhead roses
- Prevent cane borer damage
- Garden Myths – Learn the truth about gardening
- Styrofoam Cones – How Do They Work?
- Experiment Design
- Styrofoam Cones – Do They Keep Roses Warm in Winter?
- Will Sun Warm The Cones?
- Raw Data
- Winter protection for roses
- Rose cones
- Insulating fabric
- Installing insulating fabric
- Tree roses
- Rose bushes in pots
- Remove winter protection and tie in climbing roses
- A Rose Bush In Cold Weather – Care Of Roses In Winter
- Tips for Preparing Roses for Winter
- Getting Your Roses Ready For Winter
Protect Roses for the Winter
Time to Winterize: Ready Roses for Winter
Selecting roses that are appropriate for your hardiness zone is very important. But even the hardiest rose appreciates extra protection when the mercury plummets. Let’s talk hardiness first.
- Winter hardy roses are ideal for gardeners who love roses but don’t want to provide much, if any, winter protection. Roses listed in our “Winter Hardy” section meet that criteria and will provide the joy of having roses in the garden even under the most adverse conditions.
- Own root roses (the only kind we produce) are less vulnerable to winter injury. Choose from shrub roses, groundcovers, and climbers from different breeders including Griffith Buck, David Austin, and a few bred in Canada to withstand very severe cold. You will find a size and color to meet any gardening need.
- Griffith Buck, during his time at Iowa State University, developed a group of roses that could not only withstand the Iowa cold, but proved to be disease resistant, too. While other roses need protection in Zone 5, the Buck roses do not; although some protection in Zone 4 is advisable. In order for these roses to be ready to over-winter in Zones 4 and 5 they should be planted by July 1st.
Get Ready for Winter
Winterizing involves more than just covering roses with mulch. The healthier the rose, the better it will be able to withstand cold and ward off disease. Give your plants a frosty edge with these ten tips:
- Choose the right rose for your area.
- Plant it in full sun where it will receive at least 5 hours of light per day.
- Check the soil ph. It should be between 6.0 and 6.5.
- Ensure good drainage. It helps roots to establish.
- Fertilize regularly. Roses are heavy feeders and do not like to miss a meal.
- Water at ground level. Aim for 2 inches per week; more if the weather is extremely warm.
- Stop fertilizing in late summer. You want to slow down new growth, as this will enable the plant to go dormant.
- Stop deadheading in the fall to allow the rose to form hips; this is a signal to the plant that it is time to start getting ready for winter.
- Clean up the ground and the bush as old debris and leaves harbor pests and disease.
- Wait until spring to prune. You don’t want to stimulate new growth.
Winterizing Roses For Zones 7-13:
Winterize your roses by adding a 2-3” layer of mulch to insulate roses during potential cold snaps.
Three Ways to Winterize Roses For Zones 1-6:
Keep in mind that your goal is to prevent the rose bush from freezing and thawing. Winterize after you have had a couple of hard freezes. Protecting roses from the coldest, windiest months of winter is paramount to next season’s success! Your action now will reward you next spring and summer with beautiful blooms on healthy canes!
If you elect to winterize your roses, get advice from your local rose society as to what is practiced in your area. The American Rose Society website can be helpful: www.ars.org.
Pile or “hill” up loose soil around the base of the plant. Do not scrape the soil from around the plant for mounding, rather, bring in extra soil. Soil should cover the center of the rose and form a mound at least 12” high and wide. After you ‘hill’ your roses, cover the soil mounds with mulch such as straw, fir boughs or branches.
2. Rose Cones
Be sure to follow these directions carefully as Rose Cones must be used correctly to avoid damage.
There are many different options for purchase fr rose cones such as this Bio-degradable and Recyclable option from Friends of the Earth, or Rose Cone Protective Cover from Gardener’s Supply Company, or Styrofroam Rose Cones (can be found on Amazon).
First, do not cover plants too early. Follow the same timing guidelines as other methods. When using Syrofoam Rose Cones the cones need to be well ventilated so heat does not build up on the inside during sunnier winter days. Cut four or five one-inch holes around the top and bottom of the cone to aid in ventilation and to keep the air inside the cone from heating up.
Before you place the cone over the rose, mound soil up around the base of the rose (if you are trying to protect a more tender variety, you can remove more off the top of the cone and fill the inside with straw). Place a weighted object on the cone to keep it from blowing away.
3. Bending Down and Covering:
Climbers and larger Shrub Roses are more challenging to protect. In very cold climates, Climbers may need to be detached from their support and bent to the ground and covered with soil, mulch, or straw. When laying Climbers down, be careful so canes aren’t damaged or broken. If roses need to be left on their structures, straw and burlap can be placed around the canes, and the entire support structure should be wrapped and tied.
How to Protect Your Roses in the Winter
Winterizing your house in preparation for the colder months is important, but too many people neglect their gardens. Why would you let a little bit of cold weather shrivel up your gorgeous plants when protecting them is such a simple task? We decided to take charge of our blooming plant life this year by properly protecting them from Jack Frost’s fierce cold. Work fast; winter is on its way!
In areas where winter is mild, but the ground still freezes, give your roses a little extra protection during the cooler months of the year.
What You Need
- Fresh topsoil or compost
- Shredded leaves or bark
1. In early fall, stop cutting roses and let plants form hips (seedpods) as they prepare naturally for winter.
2. After the first frost in fall, protect plants from the potential damage caused by freezing and thawing cycles by piling soil over the base of the plant; cover the bud union and up to about 2 feet. Use fresh topsoil or compost, not soil scraped from around the plant. Prune overly long canes on bush-type roses to prevent wind damage. Expect a certain amount of winter kill (when canes die as far back as the bud union). Plan to prune off dead canes in early spring.
3. After the first hard freeze, add mulch: Pile dry, shredded leaves or bark chips on the mounded soil. In spring, remove the leaves or bark and the pile of soil; spread the leaves and bark around the garden.
In areas where winter brings sub-zero temperatures and frigid, drying winds, take extra precautions to help your roses survive.
- Garden fork
- Fresh topsoil or compost
- Shredded leaves or bark
1. Wrap twine around the canes to hold them erect as you work. Use a garden fork to gently unearth the plant’s roots. Dig a trench to one side of the rose large enough to contain the height and width of the plant.
2. Gently tip the plant and lay it in the trench. Cover it with soil. Pile a 2-inch layer of shredded leaves on top of the soil. In early spring, carefully uncover the rose and replant it.
Hybrid Tea Rose
Hybrid tea roses aren’t as durable as other types of roses and are susceptible to summer diseases that weaken the plant. Be sure to give them plenty of protection.
- Plastic cylinder or styrene cone
- Shredded leaves, bark, or soil
To make a rose cone, purchase a reinforced plastic cylinder or a styrene cone for each plant. Place the cylinder or cone over the plant and fill it with dry leaves, soil, or bark chips. Remove the protection in early spring.
Standard roses have their graft union near the soil line, making it easy to protect the most important part of the plant. Tree roses, however, have their graft union a few feet off the ground and need extra protection.
- Wooden stakes
- Twine or wire
1. In mild-winter areas, pile straw around the base of a tree rose. In cold-winter areas, use soil instead of straw—soil will provide more insulation.
2. Place a framework of wooden stakes around the tree.
3. Wrap a generous length of burlap around the stakes to enclose the tree. Secure the fabric using twine or wire.
4. Fill the enclosure with dry leaves or straw. In extremely cold areas, treat tree roses as you would other roses, by burying them in trenches.
Overwinter potted tree roses as well as other potted roses by moving them into an unheated garage or to a sheltered place next to the south side of your house. Protect each plant by placing it, pot and all, in a roomy cardboard box and packing the box with shredded newspaper, dry leaves, styrene packing pieces, or peat moss. Surround the box with bales of hay.
Plan now to protect your roses from the potential damage caused by freezing and thawing cycles in the winter. A little preparation now will go a long way to give your roses a little extra protection during the cooler months of the year.
If you live in Zones 1 through 6 and parts of 7, you will need to protect your roses from the damaging effects of harsh winters. Most of all, remember that healthy roses are stronger – fertilizing and watering regularly during the growing season will make your plants better able to withstand harsh winters.
Fertilize and deadhead for the last time.
October and November
Depending on where you live and how soon fall and winter comes, you’ll want to start protecting your roses for the winter. Once you have had a few good frosts, leaves will start falling. Apply a dormant spray such as lime sulfur and/or spray oil. This will kill pests and fungal diseases that might try to overwinter on the plant or surrounding soil. It can also help nudge those final leaves off. Rake leaves from around your plants to prevent the spread of diseases.
Zones 1-6 and some of Zone 7 should follow these additional winter protection guidelines:
For Hybrid Teas and Floribundas: Cover the crowns with a mound of soil about 6″ high, then cover the plants and mound with straw. Don’t prune your roses at this time, unless there is a concern that canes and branches could be broken when loaded with snow.
Tree Roses: In areas where winter temperatures are below 10°F., remove any stakes and gently dig away soil on one side. Bend your tree rose downward to the ground and cover it with straw first, then soil.
Climbing and Groundcover Roses: Cover the base of your climbers with soil. Tie the canes and wrap them in burlap. For severe-winter areas, anchor the canes to the ground and cover them with straw.
In Zones 7-8:
Protection is usually not necessary, but roses can benefit from applying mulch over the crown area if a cold winter is forecasted.
December and January
In Zones 9-11, roses usually don’t go completely dormant, but it still is a good idea to rejuvenate them at this time. Remove all the old leaves, prune out weak, spindly or diseased canes at the base, remove any canes crossing through the center, then prune remaining canes back by one-third to one-half.
Late winter – This is the time to prune your roses – killing freezes have passed and the roses are just starting to break dormancy (buds are swelling).
Water your roses if there is no rain or snow for more than two weeks, to keep roses healthy and prevent them from drying out. Be sure to remove the soil mound and any other protective covering when buds begin to swell in spring.
Tips for Pruning Roses
Roses have a reputation of being difficult to grow—as long as you feed them and prune them correctly, you shouldn’t have too much trouble with these pretty plants. Pruning is a vital element of rose plant care and the longevity of the plant in your garden. In general, you will be pruning rose bushes just before the plant breaks dormancy after spring’s final frost. This will be early in the year in warm climates, and anytime between January and April in cold climates.
If it’s old roses you are tending, prune them after blooming. They bear flowers on last year’s wood. When rose pruning, cut away the dead wood first—it will help you “see” the shape of the plant without distraction. It’s a good idea to visit a public rose garden and find specimens of roses you are growing. Note how the gardeners have pruned roses of the same type.
In cold-winter climates, pruning roses in spring is often reduced to one option: Simply cut back the wood that was killed in winter. In warm climates, pruning can be done at any of three levels, depending on your purpose. Severe pruning (cut to leave three or four canes, 6 to 10 inches high) produces fewer but larger blooms. Moderate pruning (five to 12 canes cut to 18 to 24 inches) makes for a larger bush. And light pruning (less than one-third of the plant is thinned out) increases the number of short-stemmed flowers that will be produced.
Pruning Tools for Rose Bushes
Invest in a pair of high-quality pruning shears with both blades curved. (Those with a flat “anvil” on one blade tend to crush stems, not cut them.) This is one tool where price really does make a difference. Select a manufacturer with a proven track record, and buy the best that you can afford. Some pruning shears have a special hand grip designed for left-handed people. Others have swivel handles that are easier on your wrists, and there are models with removable blades for storage. Smaller versions (costing about $20) are available for pruning miniature roses.
Next, you’ll need a pruning saw to remove large woody canes. It will give you a clean cut without damage to the bud union. The third tool you need is a pair of lopping shears. Loppers are pruners with long (12- to 18-inch) handles. They will provide you with leverage for the thicker canes. Finally, buy a good strong pair of leather gauntlet gloves or hand gloves that are puncture proof. Now, you’re ready to start trimming roses.
Related: Tips For Growing Heirloom Roses
Why Prune Roses?
Pruning intimidates some gardeners. But learning how to prune a rose bush isn’t a difficult task. When you understand the reasons for making the cuts, pruning becomes less daunting. Here are the reasons to prune.
Health: The dead or damaged canes of any rose should be cut back to green wood in late winter or early spring before the plant resumes growth. Remove diseased canes when you notice them. Improve air circulation by removing canes that grow into the center of the plant.
Appearance: Bushy Modern roses need help to maintain their compact, open form. Heirloom roses require less pruning because their lax, twiggy look is part of their charm. By fall, miniature roses have grown tall and leggy. Deadheading, or cutting off spent flowers, encourages plants to rebloom.
Control: Some roses grow with wild abandon. Trimming rose bushes removes diseased and dead stems and canes and reduces the overall size of the plant. Keep them within bounds by pruning their tips or entire canes anytime. Colder evenings produce ill-formed, mottled blossoms and yellowing foliage that often starts to fall off. Rose hips, which can interrupt the next blooming cycle, may result if spent blossoms are not removed.
Rose Pruning Principles
1. Always prune dead wood back to healthy tissue. You will recognize the living tissue by its green bark and white pith core.
2. After you make each cut, cover it with a drop of white glue to ensure qa uick recovery, as well as provide protection against cane borers.
3. Prune to ensure the center of the bush is open for maximum air circulation.
4. Remove all growth on the main canes that are not capable of sustaining a reasonably thick stem on its own.
5. If suckers—growths from the root structure that sprout from below the bud union—are present, remove them as close to the main root cane as possible.
6. Remove woody old canes; saw them off as close to the bud union as you can get.
7. After you have completed pruning your rose bush, remove any remaining foliage from the canes and clean up debris from around the bush. Discard all foliage (do not use it in the compost heap).
How to Prune Roses
1. Make your pruning cuts at a 45-degree angle, about 1/4 inch above a leaf axle with a dormant eye.
2. Choose an eye on the outside of the cane and slope the cut down and away on the opposite side. This allows excess natural sap to rise and seal the cut without interfering with the developing eye. Cutting a rose bush to an outward-facing bud also promotes outward growth, opens up the plant to air circulation, creates more pleasing shapes, resists disease, and prevents the canes from becoming a tangle. Cuts closer to the eye than 1/4 inch may damage it. Cuts higher than that will leave a visible stubble—a haven for both pests and disease.
3. If the rose bush has foliage present, the location for your cut is easy to spot. Where there is no foliage to guide you, find the dormant eye by locating where the foliage was once connected. The eye is normally visible as a slight swelling above the surface of the cane.
4. Use this same pruning technique when cutting stems for display and when removing spent blooms. For rose bush care, remember to sharpen your pruning tools periodically—either do it yourself or have someone do it who is specially trained.
5. Wipe metal surfaces after each use with a soft, lightly oiled rag to prevent rust. Store tools in a dry area.
Related: What to Prune When
How to prune roses
Pruning roses is easier than you might think.
Most roses need a little spring cleanup, whether it’s a drastic pruning or just a light trim. Take a look at the illustration above to see what you need to prune out of your roses and why. Trim off any dry, blackened, winter-damaged growth at the end of the canes, looking for an outward-facing bud. Remove crossing, rubbing branches. You’ll reduce the risk of damage to the plant and create a more open, appealling shape for the rose bush. In USDA zones 5 and colder, if there’s a graft, it should be buried 2 to 4 in. below the soil line. Cut dead or old canes off as low as you can — brushing soil away if necessary.
How to deadhead roses
Then, when roses are going strong in the summer, they’re going to need a little deadheading to keep them blooming. The photo above shows a couple of things to keep in mind as you’re deadheading a rose. See the strong new shoot? That’s where the next flower will come from. And notice that the leaf just below that bud has five leaflets? Even if you can’t spot the new shoot on a stem, it’s best to cut just above a leaf like this one. Cutting back to a leaf with only three leaflets often results in weak stems.
Prevent cane borer damage
Anytime you cut a stem that is 1⁄8 in. in diameter or larger, you run the risk of cane borers, as you can see in the photo above left. These worms eat the tender pith in the stem, weakening the plant. But you can see the simple fix in the photo above right — seal each cut with a drop of white glue and they can’t burrow into the stem.
Are you growing hybrid tea roses? Read some more specific information about how to prune them here.
Depending on your disposition, pruning roses can be seen as either the final task of winter or the first activity of spring. Either way, roses should be pruned just before they come out of dormancy and put out new growth.
In most regions of the country mid to late February is the ideal time to shape up your plants, even if you live in a mild area where roses never go dormant. If you live in a cold climate, pruning should be done when you remove winter protection and the danger of a hard freeze has passed, which may be as late as April in very cold zones. Check with your local cooperative extension or fellow gardeners for the dates they recommend.
Roses come in many forms, but whether you are growing a hybrid tea or an old fashioned climber, pruning is basically the same for each type. The hardest part is making the first cut. Here is a set of guidelines to follow that will help ensure beautiful blooms this spring.
Pruning promotes healthy, vigorous stem growth. If you stop to think about it, it just makes sense. Stronger stems result in larger blooms, while spindly growth will produce smaller roses.
Pruning removes dead, frost damaged and diseased wood, which lays the groundwork for a healthy growing season.
Pruning opens the center of the plant, promoting good air circulation, which is essential for healthy roses.
Pruning helps maintain an attractive and well-balanced shape to the plant.
In warm climate gardens, pruning creates a period of forced dormancy so your roses can rest before the growing season gets into full swing.
- Sharp Hand Pruners – For a clean cut select the bypass/scissor type and not anvil pruners. Anvil pruners are better suited for cutting back dead branches and stems.
- Long Handled Loppers
- Pruning Saw
- Heavy Gloves – Don’t skimp on the gloves. One nasty tangle with a thorny cane can bring a swift end to your love affair with roses.
- White Glue – Glue that dries clear is an easy and affordable pruning seal.
The Right Cut
For the best results you should make your cuts at a 45 degree angle, about 1/4 inch above an outward facing bud. The lower side of the angle should be opposite the bud. The plant will now direct energy to this top most bud for producing a new stem. The position of the bud on the cane indicates the direction of the new growth. By carefully selecting which bud becomes the stem producer you can manipulate the shape of the rose. Ideally, you want the rose bush to grow out, but in some cases you may want it to develop in a certain direction. This is especially true of climbing roses you want to train to grow up a trellis or over an arbor.
How To Prune
Begin by removing dead and diseased wood. Small stems can be cut back with your hand pruners, use your loppers on larger canes.
The next thing to do is remove any large, old canes and cut them at the base of the plant. Old canes will be gray and rough textured. For the best result, use your pruning saw and cut the cane flush with the bud union.
Once the plant is cleaned up, take a close look at its form. Pick out 3 or 4 of the strongest canes and remove the others.
Now cut back about 1/3 of the top growth and any crisscrossing stems to promote good air circulation. The rule of thumb is to take out stems that are smaller than the diameter of a pencil.
Remove any leaves left on the plant from last year. This will help prevent carrying over black spot and other fungi and pests from one year to the next.
Seal newly pruned stems with a white glue that dries clear, such as Elmers. This will help shed water and keep insects from getting into the center of the cane and damaging the plant.
To finish the job, pick up all the resulting debris, bag it and throw it away.
Old fashioned roses should be pruned with a lighter hand than hybrid teas. Simply remove any dead or damaged wood, the top 1/3 of growth, and crisscrossing branches.
Old fashioned roses that flower once each growing season, such as Damasks and Mosses, bloom on old wood. These types should be pruned in the summer after they have flowered.
Knockout Roses do not need to be pruned every year. In spring you can remove dead or damaged wood and shape if you wish taking out some of the ‘twiggy’ growth to improve air circulation and about every 3rd year remove about one third of the old branches to stimulate new, fresh growth. Since they are continuously flowering throughout the season, it really makes no difference when, where or how much you prune.
Garden Myths – Learn the truth about gardening
As winter approaches, we worry about our poor plants making it through the cold. All manor of wrapping devices are used to protect them and Styrofoam cones, also called rose cones, have become popular in recent years. Do these contraptions work? If they do, how much warmer do they keep your plants?
There is a lot of talk on the internet about Styrofoam cones. Many extension offices recommend them, and suppliers certainly tell you they work, but I was unable to find a single source of information that actually provided data to support the idea that Styrofoam cones keep plants warmer in winter.
So I decided to do some testing of my own.
Temperature changes with and without a Styrofoam Cone, by GardenMyths.com
Styrofoam Cones – How Do They Work?
Covering a plant, like a rose, with a Styrofoam cone will do two things. It will reduce evaporation due to reduced winds and it may increase the temperature around the plant.
The Styrofoam is thick enough to prevent wind from going through it so less wind will hit the plant. A reduction of wind, will reduce evaporation. The effect will be higher in evergreen plants than in deciduous plants since deciduous plants do not have leaves or stomata in winter – the main source of water loss.
What about the effect on temperature?
To better understand why a Styrofoam cone might increase the heat around a plant, have a look at my previous post How to Protect Plants from Frost. The only heat source is coming from the ground. Since Styrofoam is a good insulator, it should trap heat inside the cone. Let’s find out if that is really true.
Last winter, I set up the following experiment.
Instead of a Styrofoam cone I used a Styrofoam fish box as pictured below. These boxes are used to ship fish around the country and can be picked up at restaurants and grocery stores for free. The thickness of the Styrofoam in these boxes is a bit thicker than some commercial rose cones, so my container might be a bit more efficient at trapping heat than a commercial product.
Commercial Styrofoam rose cone
Most references that recommend using a Styrofoam cone to protect plants suggest putting some small holes in the cone. I am not sure if that is a requirement, but I did not do that in this experiment. The presence of holes might affect the amount of stored heat.
The Styrofoam box was set on the ground and a stone was placed on top to keep winds from moving it. The ground in this case was one of my garden beds. The soil is covered with about one inch of old wood chips. What this means is that there is not a perfect seal between the Styrofoam and soil/chips because wood chips have spaces between them.
A lab grade thermometer, accurate to 0.5 deg C was placed under the Styrofoam box, and left there. On selected days, between 10:00 am and 2:00 pm, I went out, lifted the box, and quickly read the temperature. This provided the temperature under the box. I then waited about 5 minutes for the thermometer to equilibrate to the air temperature and took the air temperature reading, making sure the sun was not shinning on the thermometer. The thermometer was then put back under the box until the next reading date.
Styrofoam fish box – do they keep roses warm, by Robert Pavlis
The 2014-15 winter was a bit unusual. We got a bit of snow – maybe 5 cm (2″) in early January, but it did not stay around. The rest of January was cold, but mostly snow free. There was no real accumulation of snow until the first of February, when we received 10 cm of snow. New snow fall during the rest of February ensured that we had at least 10 cm of snow on the ground at any point, and most days it was more. The amount of snow was never enough to cover the Styrofoam box.
By early March the snow was melting and the experiment was stopped on March 13.
The above chart shows the results.
In January the temperature under the box and in the air were almost the same. On very cold days the temperature under the box was slightly warmer by about 2.5 degrees. On warmer days both temperatures were about the same.
In February two observations were made.
- The temperature under the box stayed warmer in February than in January, with a low of -6 deg C.
- The difference between inside and outside the box was greater in February (delta=7 deg) than in January (delta = 1 deg).
Styrofoam Cones – Do They Keep Roses Warm in Winter?
The answer is yes and no.
On two testing days, the temperature under the box was actually colder than the air temperature. The differences were small and can be explained by the fact that the Styrofoam box is an insulator. Changes in temperature will happen more quickly outside the box than inside the box. If the air suddenly warms up (either a warming trend or a sunny day) the air warms faster outside the box then inside the box.
On most days the temperature was warmer under the Styrofoam box than outside the box. Clearly the Styrofoam box does keep plants warmer, most of the time.
Why is January so different from February?
The months have nothing to do with it. February had the lowest air temperatures but January had the lowest temperatures under the box. The Styrofoam box worked better in February than in January. Why?
The difference between January and February, was the snow cover which did two things.
The snow on the ground made an air seal between the ground and the Styrofoam box. In January there was little or no snow and the seal between the box and the ground was not very good. Wind could easily blow under the box and remove any heat being held in by the box. Even if there was no wind, heat can more easily escape through gaps around the bottom edge of the box. It is similar to leaving your front door open a crack in winter – makes it hard to heat the house.
In February, a heavier snow fall made a good seal between the box and the ground. After each measurement, I was careful to make sure the snow was back in place to maintain the seal for the next reading. With the snow in place, the wind had no way to reach the inside of the box and cracks along the bottom edge of the box were sealed.
A second factor was also at play. With no snow on the ground, the ground around the box would cool off to the same temperature as the air, or very close to it. With no snow, the surface of the soil around the box was cold, making it harder for the box to keep the soil under the box warm. Once snow was on the ground the soil inside the box and outside the box were both warmer than the air, making it easier for the box to maintain it’s warm temperature.
These explanations may not be entirely correct, but they do follow basic thermodynamic principals. It is clear that the snow cover caused the difference.
Styrofoam cones do keep the air under them warmer in winter, provided that there is a good seal between the soil and the cone. In areas that do not have reliable snow fall, it would be a good idea to use soil around the cone to make the seal.
Styrofoam cones will not prevent the plant inside the cone from reaching freezing temperatures. In zone 5 (location of this experiment), a low temperature of at least -6 deg C should be expected.
Will Sun Warm The Cones?
The Iowa State University, in an article called “Preparing Roses for Winter” (ref 1), claims that “air temperatures inside the cones may get quite warm on sunny, mild winter days without ventilation holes. ” Other sites also make this claim.
Is it true?
The experiment in this post did not look at this point. However, on the warmest day in January, and on the warmest day in Feburary/March, the temperature under the box, was cooler than the air temperature. This suggests that the box actually keeps plants cooler on warm days.
This does make sense. If you take a Styrofoam cooler full of beer to the beech, the inside of the cooler stays colder even in the sun. Styrofoam is an insulator, which means it keeps the warmth of the sun out of the box.
The ground can still be frozen on a sunny warm winter day – warmth is relative – 0 degrees is warmer than -6 degrees. The Styrofoam cone will help keep the ground frozen, and keep the plant cooler, on a sunny day.
On a warm sunny day, ventilation holes will tend to warm up the inside of the box since it will let warm air enter. Do you poke holes in the lid off your cooler to keep the beer colder? Only when you’ve had too many!
This is not proof that the statement by the Iowa State University is wrong, but I think basic physics suggests it is wrong.
Adding the holes may still be a good idea to allow ventilation of humidity in very early or very late winter – I don’t know.
The following is the numerical data for this experiment.
Styrofoam cones, temperature data
- “Preparing Roses for Winter” by Iowa State University; http://www.extension.iastate.edu/article/yard-and-garden-preparing-roses-winter
- Photo of commercial Styrofoam rose cone: Rona Inc
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Winter protection for roses
Winter protection is a way of sheltering your plants from abrupt temperature variations (freezing and thawing). Native and naturalized roses as well as most modern shrub roses do not require any protection apart from a good layer of snow. Less hardy or grafted roses (hybrid teas, floribundas, etc.) must be protected if they are to survive the winter.
- Before installing winter protection, cut the canes back to 30-35 cm above the soil.
- Place all leaves and pruning debris in the garbage (do not compost).
If planting in autumn, mound soil up around the base of hardy plants. This will protect them from the autumn cold and from sunburn in spring. After all risk of spring frosts is past, gently remove the mound of soil and lightly spray the canes with a hose to clean them.
Prune canes, remove leaves and mound soil up around the base of the plant to a depth of 20-25 cm. Anchor the cone firmly with a brick or stakes. In our climate, the efficiency of such cones depends on the snow cover (40 cm is ideal).
Such fabric, a sheet of Styrofoam covered in opaque white plastic, will help protect your plants by keeping the temperature constant. It is well suited to mass plantings, climbers and standard or tree roses. There is no need to mound or bury the plants beforehand.
Installing insulating fabric
Remove the leaves from the plants and clean all dead leaves from beds to prevent fungal diseases. First build a frame out of stakes or chicken wire. Then wrap the fabric around the frame and attach it firmly.
Install the protection in autumn (mid- or late November) when the plants are dormant and after a few days of –5ºC to –10ºC temperatures. Remove the protection in spring, around mid-April, once the soil thaws.
Remove the leaves and untie the branches. Lay them delicately on the ground to form an arch and tie them together. Build a frame over the plant and cover with the insulating fabric.
Dig out the bush with the basket. Lay on the soil and mound the roots. Build a frame and cover with the insulating fabric.
Rose bushes in pots
Keeping rose bushes in pots on a balcony in the wintertime is risky. Snow accumulation plays a major role in plant survival. Exposure to cold winds and extreme variations of temperature (freezing and thawing) often cause the death of poorly protected plants. If you don’t have the choice, prune the rose bush and remove the leaves. Place it in a Styrofoam insulated box and fill it with dry leaves. Place the box near the wall and cover it with snow, the best winter protection.
Remove winter protection and tie in climbing roses
Remove winter protection as soon as the weather permits, because plants may get overheated under insulating cones and fabric. Moisture build-up underneath can also promote certain fungal diseases. Whenever possible, choose a cloudy day or wait until late in the day. Buds that have spent the winter under protection are easily burned or dried out by a sudden change in conditions. Keep protective covers handy and replace them if there is a threat of late frost.
Wait a few days before tying climbing roses to supports. The stems will be more flexible once they have had a chance to adapt to the new weather conditions.
Grafted roses that were buried in a trench for the winter should be replanted once the ground has thawed sufficiently. Choose a sunny site and rich, well-drained soil. Don’t forget to stake the plant on the prevailing-wind side.
Wait about 10 days before pruning your roses. Any buds that are unable to survive the transition will have time to show signs of dieback.
A Rose Bush In Cold Weather – Care Of Roses In Winter
By Stan V. Griep American Rose Society Consulting Master Rosarian – Rocky Mountain District
Even though it is a tough thing to do, in many areas we need to let our rose bushes take their winter nap. To make sure they go through the winter well and come back strong the following spring, there are a few things to do and keep in mind.
Tips for Preparing Roses for Winter
Starting Care of Roses in Winter
Proper care of roses in winter actually starts in summer. I do not feed my roses any further granular fertilizer after August the 15th. One more feeding of a multipurpose foliar applied fertilizer towards the end of August is okay but that is it, the reason being that I do not want the rose bush still growing hard when the first hard freeze comes as that can kill the bush. Stopping fertilizing is a kind of winter protection for roses.
I stop deadheading or removing the old blooms by the end of August as well. This too helps give a message to the rose bushes that it is time to slow down and put some energy into their winter reserves. The next step for roses’ winter care is around the first week of September. I give each rose bush 2 or 3 tablespoons of Super Phosphate. It moves slowly through the soil and, thus, gives the roots something to keep them strong during the sometimes long and hard winter and will help the rose bush survive cold weather.
Pruning Roses for Winter
Once a couple hard frosts or freezes have hit the garden, the rose bushes will start to go dormant and you can start on the next step in preparing roses for winter. This is the time to prune the canes on all the rose bushes, except the climbing roses, down to about half their height. This helps keep the canes from being broken over badly by heavy winter snows or those nasty whipping winter winds.
Mounding as Winter Protection for Roses
For care of roses in winter, this is also the time to mound up around the grafted rose bushes with garden soil and mulch, rose collars filled with mulch, or whatever your favorite mounding medium is to protect the rose bush in cold weather. I mound up around my own root roses too, just for good measure but some folks do not. The mounding is to help keep the graft and bush hold once things have turned cold.
The temperature fluctuating between hot and cold can confuse the rose bushes and cause them to think it is time to grow while still winter. Starting to grow too soon and then getting hit by a hard freeze will spell death for the rose bush that has started to grow early. The climbing rose bushes should be mounded as well; however, since some climbers bloom on the old wood or last year’s growth only, you would not want to prune them back. The climbing rose bush canes can be wrapped with a light fabric, available at most garden centers, that will help protect them from the harsh winds.
Watering Your Rose Bush in Cold Weather
Winter is not the time to forget about the rose bushes needing water. Watering roses is an important part of roses’ winter care. Some winters are very dry, thus the available soil moisture is quickly depleted. On the warmer days during the winter, check the soil and water lightly as needed. You do not want to soak them; just give them a little drink and check the soil moisture again to see that it has improved. I use my moisture meter for this, as it gives me a good feel for the soil moisture and works better than a cold finger!
We have had winters here where it snows well and then starts to melt due to a string of warm days, then all at once we get a hard freeze. This can form ice caps around the rose bushes and other plants that will stop the travel of moisture down to the root zone for some time. This can starve the rose bushes and other plants of valuable moisture. I have found that sprinkling Epsom Salts over the top of the ice caps helps make holes in them during the warmer days, which allows moisture to travel through again.
Winter is a time for our roses and us to rest a bit, but we cannot totally forget our gardens or we will have much to replace in the spring.
Getting Your Roses Ready For Winter
Rose Hips in winter
Photo/Illustration: Paul Zimmerman Roses Rose Hips in winter
Photo/Illustration: Paul Zimmerman Roses
Fall is in the air here in the upstate of South Carolina and this means it’s time to start thinking about preparing your roses for winter. It doesn’t mean they won’t keep blooming for a while as my roses often flower into Thanksgiving. However, a frost or freeze can come at anytime so let’s be ready so it won’t damage your roses going into winter.
First, it’s time to stop fertilizing with anything that is high in nitrogen, which is the first number on the NPK scale. Those are the numbers you see on fertilizer packages like 10-10-10. Nitrogen promotes growth and what we don’t want right now is new tender growth popping up that could be harmed in a frost or freeze.
Jack Falker, who writes a great blog called A Minnesota Gardener, recently did a post on Winter Protecting Your Roses. He has over 20 years experience growing roses in Minnesota and one of the things he’s learned is to stop the fertilizers and instead feed your roses potassium once a week for six weeks before your first average hard freeze date. Generally you can find that date by googling your location with the words “first average freeze date”. If you don’t get it at first try a larger city near you.
Jack says in his post that potassium blocks the growth-promoting affects of nitrogen and phosphorous thereby hardening the canes off for the winter. This is an excellent idea and will counter the affects of any lingering nitrogen in the soil or the plants.
You can buy it from your local garden center or farm supply place if you live in a rural area like I do. Simply follow the directions on the package. There are liquid and granular forms, but whichever you use make sure the first two NPK numbers are zero. Something like 0-0-23.
It’s also time to stop deadheading or cutting off the old blooms. Just let them fall off naturally so the rose can start setting hips. Hips are the “berries” you often see on roses in wintertime. Generally they are orange but some roses produce reds or yellows as well. In actuality they are seed pods, and when they’ve set the rose feels like it’s done it’s job of “reproducing” and can now stop creating new flowers and the new growth needed to produce them. This is another important part of letting your roses go to sleep for the winter.
As your roses begin to shut down, stay a little extra vigilant about cleaning dead or damaged growth. We don’t want that on our roses over the winter as it invites disease and other potential problems.
Roses are quite strong and with a little extra help from us they should sail through winter with no problems. In the coming months we’ll talk about some other things you can over the winter so stay tuned!