Hardy shrub roses get through a New Brunswick winter with little fuss. That means the rugosas, the Explorer series bred in Canada, and a few tough modern shrubs such as Knock Out. Hybrid teas, tree roses and many English-style roses sold at garden centers need real winter help. If you are new to the plant itself, start with growing roses in New Brunswick. Sorting the roses that stay put from the ones that don’t saves money, and it means what you plant in spring is still alive next June.
Which roses survive a New Brunswick winter
Moncton, used here as a reference point for southeastern New Brunswick, sits in Canadian hardiness zone 5a, according to Natural Resources Canada and its maps built on recent 30-year normals. That is a Canadian zone, and it does not convert to a USDA zone. The Canadian system blends seven climate variables, while the USDA system uses one. Natural Resources Canada says plainly that there is no simple conversion, and its own example is Canadian zone 4a, which overlaps nine USDA zones, from 3a to 7a. A tag reading “zone 5” on a rose from a U.S. grower is probably a USDA zone, so check which system printed it.
Moncton is also one city, not the whole province. Northern and upland districts run colder and stay frozen longer, so a gardener there should treat 5a as a ceiling and not a promise.
Environment and Climate Change Canada’s climate normals for the Moncton station put the average last spring frost on May 19 and the average first fall frost on October 2. Those are midpoints. In one year out of two the last frost lands after May 19, and in one year out of two the first fall frost arrives before October 2. Treat both dates as the middle of a window. For roses, the fall end matters most. A plant needs time to slow down and harden its canes before the ground freezes.
Which types of roses handle zone 5a without help?
Rugosas lead the list. They have thick, prickly canes, wrinkled leaves and a tolerance for cold, wind and road salt that few other roses match. That salt tolerance is a real asset in coastal parts of the province. The Explorer series was bred in Canada specifically to take cold, and its shrubs and climbers usually need little more than a tidy-up in spring. The Parkland roses, developed for prairie winters, belong in the same camp. Species roses and many old shrub roses also cope well, though they bloom once a season.
Where do hybrid teas fall short in zone 5a?
Hybrid teas, grandifloras and most floribundas were bred for milder winters. Most carry hardiness ratings that start at a zone warmer than 5a, which puts them at the edge of survival in a typical winter. In a hard one, the canes die back, and in an open, windy yard the whole plant can go. Snow cover helps a great deal, because buried canes are insulated, but a hybrid tea that depends on snow is a gamble. The extra work they need is covered in Protecting Roses Through a New Brunswick Winter.
Named roses that hold up here
Most of these can be found at independent nurseries and through mail-order Canadian growers. Prefer the rugosas and Explorers if you want a rose you can forget about from November to April.
| Rose | Type | What it survives |
|---|---|---|
| Hansa | Rugosa shrub | Rated for colder zones than 5a; takes wind and salt spray; reblooms and sets hips |
| Therese Bugnet | Hybrid rugosa shrub | Bred in Alberta for prairie cold; little dieback in zone 5a |
| William Baffin | Explorer climber | Canes carry through zone 5a winters; tall and vigorous |
| John Cabot | Explorer climber | Hardy in zone 5a; needs no cane protection in most winters |
| Knock Out | Modern shrub | Survives zone 5a, but canes often die back in cold winters and regrow from the base |
| New Dawn | Climber | Borderline; canes may die back in hard winters, but it reblooms on new growth |
Which named roses are the safest bets?
Hansa and Therese Bugnet are the two to start with. Both are rugosa types, and both have a long record in cold gardens. Hansa is a dense, suckering shrub with a strong clove scent, and it reblooms. Therese Bugnet is a taller, arching shrub with soft pink flowers and few thorns for a rugosa. Among climbers, William Baffin and John Cabot are Explorer roses with a track record in cold gardens, and neither is likely to die back to the ground in a normal winter.
Do Knock Out and New Dawn hold up in zone 5a?
Knock Out is one of the best-selling shrub roses in North America, and it does survive zone 5a. The caveat is that in cold winters the canes die back, sometimes to the snow line or lower. Because it blooms on new growth, it recovers by summer, though you should expect to prune out dead canes every spring. New Dawn is a climber that sits right at the edge of 5a. It has a good record in sheltered spots against a south or west wall, but it is not as dependable as the Explorer climbers in an open yard. A winter that kills some of its canes will cost you early flowers, though it still reblooms later in the season.
Sold here, but not for this zone
Garden centers here stock nationally, and the buyers who order the roses are not working from a Moncton hardiness map. Plenty of what sits on the shelf in April was bred and grown for zones that never see a New Brunswick January. Here are the types most likely to disappoint:
- Hybrid teas in long-stemmed colors, the classic florist rose. Most are grafted and often die back to the graft union, or die outright, in an average winter without protection.
- Tree roses (standards), which are a rose grafted on top of a trunk. The trunk and the bud union above it are the weakest points and are exposed to the full cold.
- English-style shrub roses, many of which are rated for a milder zone than 5a and get cut back hard by cold winters.
- Miniature potted roses sold in spring as gifts. These were forced in greenhouses for indoor color and often fail in a first outdoor winter.
Which of these can still be grown?
Gardeners do grow hybrid teas here, and some do it well. The price is annual work. When the ground begins to freeze, mound the crown with soil to cover the graft union and the base of the canes. Tree roses are harder, since the whole plant has to be tipped, buried or wrapped. If the plant is a gift or an impulse buy and you want it to last, expect to protect it every year and to lose it in the harshest winters.
What does the label tell you about risk?
A grower’s tag may read “hardy to zone 5” and be perfectly accurate for the USDA system while being too optimistic for a Canadian zone 5a garden. Treat any rose rated at the edge of your zone as a plant that needs protection. A rose rated for two or more zones colder than yours is the one to plant and forget.
What to check on the label before buying
Three things on a rose label or bare-root bag tell you most of what you need to know: the grade, whether the plant is grafted or own-root, and the hardiness rating.
What do grade and graft mean on a rose tag?
Bare-root roses are graded by size and by the number and thickness of the canes. Grade No. 1 is the top grade, with the strongest plants. Lower grades, such as No. 1½ and No. 2, are smaller and slower to establish, which is a handicap when winter arrives early. Grafted roses are made by joining the variety you want onto the roots of a different, vigorous rose. The swollen knob where the two meet is the graft union. Own-root roses grow on their own roots, with the variety you bought from top to bottom.
Why does own-root matter more the colder it gets?
In a mild climate, a graft union stays alive through the winter and nobody thinks about it. In a cold one, the canes and the union are the first to die. If a grafted rose dies back above the union, the new shoots may be the variety you bought. If the union itself dies, whatever grows back is the rootstock, usually a rose you never wanted. An own-root rose that freezes to the ground regrows true to its name from below the soil. In zone 5a, choose own-root plants whenever the nursery offers them. Rugosas and Explorers are normally sold that way.
Checking this against your own county
The Moncton numbers describe one place. A garden on a hilltop, a river valley or the northern shore can sit a full zone away. The provincial agriculture department can point you to growers and advice for your area, Agriculture and Agri-Food Canada is the federal department whose breeders developed the Explorer and Parkland rose series, and local nurseries know what has actually lived through recent winters. Natural Resources Canada’s hardiness site lets you search by municipality, so look up your own town before you buy. If your zone comes out colder than 5a, move down the list toward rugosas and Explorers.
Common questions
What is the hardiest rose for New Brunswick?
Hansa and Therese Bugnet are two of the hardiest roses you can buy. Other rugosas and the toughest Explorer and Parkland roses are in the same league. Any of these will get through a typical winter here with no protection.
Do Knock Out roses survive New Brunswick winters?
They survive in zone 5a, but the canes often die back in cold winters and the plant regrows from the base. Cut out the dead wood in spring and the shrub will bloom again by summer. In colder districts, expect more dieback.
Can I grow hybrid teas in New Brunswick?
Yes, with winter protection every year. The usual method is to mound soil over the graft union once the ground starts to freeze. Without it, many hybrid teas die in an average winter. An own-root hybrid tea is a safer buy if you can find one.
Do rugosa roses need winter protection?
Not in zone 5a. Rugosas, including Hansa, are hardy in a Moncton winter. A young plant in its first winter in an exposed spot may benefit from a layer of mulch, but established plants need none.