Yes, for most roses grown in Massachusetts, a mound of soil over the base of the plant is what gets them through winter. Grafted hybrid teas, floribundas and grandifloras need it in most of the state, and it is cheap insurance even on the coast. Tough own-root shrub roses can often skip it, especially near the coast. Start after several hard freezes, not on a set date. Use bagged soil and pile it about 10 to 12 inches deep, enough to bury the graft union. The details below change with your zone and your town’s elevation.
Do roses need winter protection in Massachusetts?
The state spans USDA hardiness zones 5a-7b. The USDA system rests on one number, the average coldest night of the year. A garden in the Berkshire hills and one on the waterfront in Boston are nearly two different climates for a rose. The answer to “do I need to protect it?” depends on which end of that range you garden in, and on whether the rose is grafted.
Most hybrid teas, floribundas and grandifloras are grafted. A cultivar is joined to a tougher rootstock at a knob near the soil line called the graft union. If a hard winter kills the canes above it, the plant can still send up new shoots, but those often come from the rootstock. You end up with a vigorous rose that isn’t the one you bought. Protecting the union is the main point of winter care.
| Area | Typical zones | Grafted roses | Own-root hardy shrub roses |
|---|---|---|---|
| Coast, Cape and islands, Boston waterfront | Mostly zone 7 | Mound as insurance; mild winters may pass without loss | Usually no protection needed once established |
| Inland suburbs, Worcester hills, Connecticut River valley | Mostly zone 6 | Mound every year | Usually fine; protect young plants |
| Berkshires and higher hills | Zones 5 to 6 | Mound every year and add a boughs topping | Protect young plants and exposed sites |
Which roses can skip winter protection in Massachusetts?
Own-root roses, which are grown from cuttings and have no graft union to lose, can go bare in much of the state. Rugosas and many modern landscape shrub roses fall in this group. On the warm coast the honest answer for them is no, they don’t need it. Where a winter kills their canes, they regrow true to type from the base.
Two exceptions apply even in the mildest zones. A rose in its first winter has a shallow root system and benefits from a mound. So does any rose in an open, windy spot, where drying wind does as much damage as the cold. For help choosing roses that need little fuss, see Roses That Hold Up in Massachusetts. For the basics of the whole subject, start with growing roses in Massachusetts.
When to start, and what triggers it
The trigger is a run of hard freezes. A single frost doesn’t count, and neither does a date on the calendar. A rose needs to go fully dormant before it is covered. If you bury it while the soil is still warm and the plant is still pushing growth, you smother tissue that is alive and wanting air. That is how crowns rot under a mound.
The first fall frost at Boston’s Logan Airport station falls between November 3 and November 14, according to the NOAA NCEI Climate Normals (that range is the 30 to 70 percent probability band for a 32°F freeze). Logan is a waterfront urban station and one of the mildest spots in the state, so treat it as the late edge. Inland suburbs and the Berkshires freeze earlier. Inland and in the hills, expect it to come sooner, sometimes by weeks.
How do you know a rose is dormant enough to mound?
Watch the plant and the ground rather than the date. Nights should have dropped to freezing or below several times in a row, with days staying cool. The leaves should be yellowed, dropped or blackened by frost. No fresh red shoots should be showing, and the top inch or so of soil should feel stiff in the morning. When all of that is true, mound within the next week or so. The ground does not have to be frozen solid.
Preparation happens earlier. Stop fertilizing as the season winds down so the canes harden off instead of pushing soft new growth. Buy your bagged soil before garden centers clear out their stock for the season, and stack it near the beds. Waiting until the first snowfall means digging bags out of a drift, or doing without.
Spring has its own timing. Pull the mound back in stages once hard freezes are behind you. At Logan the last spring frost falls between April 1 and April 8, and it comes later inland and in the hills. Many gardeners take their cue from forsythia in bloom. Keep a sheet or frost cloth handy for a late cold night after the soil is off. Pruning starts after the mound is gone, and When to Prune Roses in Massachusetts covers that step.
How to mound, and how deep
The job is to bury the graft union, the swollen knob at the base of a grafted rose, under loose soil. The canes don’t need to be buried. They may die back to the soil line in a hard winter, and that is acceptable as long as the union and the bottom few inches of living wood survive beneath the mound. Make the pile about 10 to 12 inches deep, shaped like a cone, so it covers the union and the base of every cane.
First, clear fallen leaves and debris from around the crown, since spent rose leaves can carry disease spores through winter. Tie the canes loosely together with soft twine. If they are tall enough to whip around in winter wind, trim them down so they don’t loosen the crown. Then pour the soil on by hand or with a small scoop, working it down into the gaps between canes.
Why use bagged soil instead of soil from around the plant?
It is tempting to scrape soil from the bed. Resist that. Digging beside a rose cuts its shallow feeder roots and leaves a hollow ring around the crown. That ring collects meltwater and freezes, which is the opposite of what you want. Soil from the bed may also carry the same disease organisms you just cleaned off the leaves. Bagged topsoil, or a topsoil and compost mix, arrives clean and loose, and it drains. It leaves the roots undisturbed. Pure compost can stay soggy all winter, so keep it as a minor part of the mix. Whatever you don’t use goes into the garden in spring.
What goes on top of the soil mound?
Once the mound itself has frozen on the surface, add a loose topping of evergreen boughs, straw or shredded leaves. It doesn’t need to be thick. Its job is to hold snow in place, shade the mound from winter sun, and slow the cycle of thawing and refreezing that can heave a young plant. Prunings from pine, spruce or fir work well, and many households have them after the holidays. Climbers can stay on their supports with only the base mounded. In windy spots on the coast, a burlap screen on the exposed side cuts the drying and salt spray.
What does not work in this climate
Massachusetts winters swing. A January thaw can bring a stretch of mild days, then the temperature drops hard again. Most protection that fails here fails because it holds in heat or moisture during those swings.
Why do plastic wrap and sealed rose cones hurt roses?
Plastic wrapped around canes traps moisture against the bark. On a sunny day the air inside warms well above the outside temperature, the canes wake up, and condensation collects. When the cold returns, that wet tissue freezes and splits. Gray mold and cane canker then have exactly the damp conditions they like. A sealed foam rose cone does the same thing. Massachusetts’ winter swings make it a poor fit. If you use one at all, cut vents in it and set it in place only after the ground has frozen, so it keeps sun and wind off the canes without building a greenhouse.
The third mistake is the quietest. Piling mulch, leaves or straw around a rose while the ground is still warm keeps the crown warm and damp, and the plant never hardens off. Voles and mice also move in, since a deep warm pile is an ideal winter nest, and they chew bark at the base. The fix is simple: wait until the ground has frozen on top before adding any insulating layer. Do the soil mound first, as described above, and the mulch comes afterward.
Checking this against your own county
The dates and zones here come from broad ranges, and your yard may sit well to one side of them. UMass Extension offers garden guidance for Massachusetts, and its Extension staff can help you compare local conditions with these reference dates. Elevation matters more than most people expect. A town in the hills can run noticeably colder than a valley town a few miles away, with earlier fall frost and a later spring thaw. Low spots where cold air pools can behave like higher ground. Write down the date of your first hard freeze each fall, and within a couple of seasons you’ll have a better trigger than any regional average.
Common questions
Can I use leaves instead of soil to cover the graft union?
Leaves alone are a weak substitute. They mat down, hold water, and make a good nest for rodents. Use soil to cover the graft union, then add leaves or boughs on top as insulation once the ground has frozen. Shredded leaves hold up better than whole ones.
Do own-root shrub roses need mounding?
Established ones usually don’t, especially in the warmer parts of the state. If a hard winter kills the canes, the plant regrows true to type from the base, because there is no graft to lose. Young plants in their first winter and roses in exposed spots are the cases where a mound is still worth the effort.
Should I water roses before winter?
If the fall has been dry, give the roses a deep soaking before the ground freezes. Moist soil holds heat better than dry, and winter wind dries out canes that have too little moisture to draw on. Stop once the soil begins to freeze, and don’t water a mounded rose through the winter.
When do I take the mound off in spring?
Remove it in stages once the worst freezes are over. At Logan the last spring frost comes between April 1 and April 8, and later inland and in the hills. Pull back the topping first, then the soil gradually, and keep frost cloth ready for a cold snap. Once the mound is gone you can look at what survived and plan pruning.