Yes, in nearly all of Vermont. The USDA Plant Hardiness Zone Map puts the state in zones 3b to 5b, and grafted roses such as hybrid teas, floribundas and grandifloras need a mound of soil over their base to get through it. Tough own-root shrub roses often manage without. The work comes late, after a run of hard freezes, and a few mistakes (plastic, sealed cones, early mulch) can do more harm than leaving the plant bare.
Do roses need winter protection in Vermont?
The USDA system rates a place on one variable only, the average yearly extreme minimum temperature. Vermont spans 4a to 6a on the 2023 USDA Plant Hardiness Zone Map. In the mildest part of the range, the coldest night of an average winter still falls well below freezing. In the coldest part of the range, winter nights are far more severe. Burlington, on Lake Champlain, sits in the milder Champlain Valley and serves as the reference city here. The Green Mountains and the Northeast Kingdom run colder, so a rose in Burlington and one in a hill town are living through different winters.
What actually kills a rose in a Vermont winter?
A grafted rose is two plants in one. A showy hybrid top is joined to a sturdy rootstock, and the joint, called the graft union, sits right at the base of the plant. That knob is the part you must keep alive. Canes can die back to the ground and the rose will still regrow if the union and roots survive. If the union dies, the plant is gone, or the rootstock sends up plain wild-rose shoots that look nothing like what you bought.
Raw cold is only part of the damage. Vermont winters swing. A January thaw softens the soil, then a hard freeze follows, and the freeze-thaw cycle heaves shallow roots and strips moisture from exposed canes. Deep snow insulates a plant nicely, but snowfall is unreliable in early winter, which is exactly when the plant is most exposed. A soil mound does the insulating job whether or not the snow shows up.
Which roses can skip the work?
Own-root roses, which grow on their original roots with no graft, can lose every cane to winter and still sprout from the ground in spring. Very hardy shrub types often need nothing beyond a layer of snow, though they may lose cane tips. Hybrid teas and other grafted garden roses are the ones that need a mound across the state, even in the Champlain Valley. For siting and general care, see growing roses in Vermont.
When to start, and what triggers it
The trigger is a run of hard freezes. A single frost is not enough. At Burlington, the first fall frost falls between October 3 and October 13, based on the NOAA NCEI 1991-2020 Climate Normals for freezing temperatures at 32 F (station data here). That date marks the end of the growing season. It is also far too early to mound, because soil piled over a plant that is still active keeps it growing, and soft new growth is what the next hard freeze kills.
In the hills and the Northeast Kingdom it arrives sooner. Go by the plant and the weather rather than the calendar.
How do you know the rose is dormant?
Look for four signs. The leaves have yellowed and dropped, or can be stripped off easily. No fresh green shoot tips are forming. Several nights in a row have dropped well below freezing. And the top inch of soil is stiff in the morning, even if it softens by afternoon. When all four line up, the plant has shut down and is ready.
The window is short, because soil that has frozen solid is nearly impossible to move. Buy the soil in October and keep it in the garage or a shed. Bags stored indoors stay loose and workable when the ground outside turns hard.
When do you take the mound off?
Spring needs the same patience. Start pulling the soil back as the ground thaws, working in a few steps over a couple of weeks. At Burlington the last spring frost falls between April 30 and May 10, and the hills run later. New shoots under the mound are pale and tender, and a hard frost on freshly exposed growth burns them. Keep the soil or a few evergreen boughs close by so you can recover the base on a cold night. Once the shoots turn green and the risk has passed, spread the leftover soil through the bed.
How to mound, and how deep
Start with a short cleanup. Rake fallen leaves away from the base, because old foliage carries disease into spring. Tie the canes loosely together and trim them to a manageable height so winter wind does not whip the plant and loosen its roots. Save the real pruning for spring, when you can see which wood is alive.
Then build the mound. The graft union is what gets buried, and the canes are left above. Cover the graft union with soil, shaped into a cone about 10 to 12 inches high that hugs the base and extends a little past it on every side. Stopping short, with a few inches of soil thinly spread over the base, leaves the union exposed to the first deep cold snap. Most of the canes will stick out of the top and may die back, which is normal. In spring you cut them back to live wood.
What should you mound roses with?
Use bagged soil, such as topsoil or a topsoil and compost mix, rather than soil scraped from around the plant. Digging beside a rose cuts and exposes its shallow feeder roots just before the ground freezes. It also leaves a shallow trench that collects meltwater, and that water freezes around the base of the plant, exactly where you are trying to keep things steady. Soil taken from the rose bed can carry fungal spores that overwinter on the surface too. Clean bagged soil avoids all three problems, and when it has been kept indoors it is easy to pour and shape.
A few bags per plant usually does it. Once the mound has frozen on top, you can add a loose layer of evergreen boughs, straw or shredded leaves over it. This holds the soil in place and catches snow. Keep that layer light. Its purpose is to hold the cone together and keep the freeze steady, and the soil underneath does the protecting.
What does not work in this climate
Three popular moves can do more harm than good. All three trap moisture or warmth around a plant that needs to stay cold and dry, and Vermont’s temperature swings make that worse.
Does plastic wrapping protect roses?
No. Plastic does not breathe, so moisture condenses inside it. On a sunny day in winter or early spring the air under the wrap heats up, and the canes start to wake. Then the temperature crashes overnight and the buds die. The damp stays against the bark, and that is how rot and mold take hold. Burlap is a better wrap for exposed canes, because it blocks wind and still lets air through.
Should you leave a rose cone sealed?
Rose cones are the foam covers sold every fall. A sealed cone works like a small greenhouse and has the same problem as plastic wrap. It also protects only the canes and leaves the base, the part that matters, exposed to the cold. Mice and voles like the dry, insulated space inside, and they chew the bark. Never seal a rose cone or wrap canes in plastic. If you use a cone, mound the soil first and cut ventilation holes in the cone, or skip it entirely.
Can you pile mulch while the ground is still warm?
Mulch put down in October, while the soil still holds summer warmth, insulates that warmth instead of the winter cold. The plant stays active, and the crown stays damp, which invites rot. Voles move into a thick blanket of mulch and eat the bark off the lower canes all winter. Put mulch on only after the ground has frozen, and keep it loose and shallow.
Checking this against your own county
Frost dates and zone numbers shift from town to town in Vermont, and elevation is the main reason. Cold air settles in valley floors, and a farm a few hundred feet higher than the next town can see frost weeks earlier in fall and later in spring than the Burlington dates above. Check your own town’s frost dates and zone with the University of Vermont Extension office, which can tell you how your site compares with the valley numbers. Use it to adjust your mounding date by a week or two, and watch the plant and the soil before you commit.
Read your location the same way you read the plant. A south-facing slope next to the house warms faster than an open lawn, and so does a rose near a foundation wall.
Common questions
Should I prune my roses before winter?
Only lightly. Trim the canes enough to stop the wind from whipping them and to make the mound easy to build. Hard pruning in fall can push new growth. Wait until spring, when you can see which canes are green and alive, and cut back to healthy wood.
Can I use wood chips or leaves instead of soil?
Soil is the better choice for the mound itself. Wood chips hold water against the crown, and whole leaves mat down into a soggy layer. Shredded leaves, straw or evergreen boughs work well as a loose top layer once the mound is built and the ground has frozen.
What about climbing roses?
Climbers carry long canes that stand fully exposed to winter wind. If the canes are flexible, unpin them from the support and lay them along the ground. Mound soil over the graft union at the base, then cover the canes with evergreen boughs. Stiff, older canes can crack, so bend them gradually or leave them on the support.
How do I tell if my rose survived?
Wait until buds should be leafing out, then scratch a cane with a thumbnail. Green under the bark means the cane is alive, while brown and dry means it is dead. Cut dead wood back to the first live bud. If the whole top is dead but new shoots appear from above the graft union, the plant lived. If shoots appear only below the union, they come from the rootstock and will not match the original rose.