The lowest temperature roses tolerate depends on the rose type and how you grow it. Most garden roses handle -10°F (-23°C) with some protection. Cold-hardy shrub roses bred for northern climates survive -35°F (-37°C) or colder with just mulch and snow cover.
Rose cold hardiness differs a lot between rose types. I've watched my hybrid teas die back to the ground at 10°F (-12°C) while my shrub roses came through -20°F (-29°C) without losing a single cane. The type of rose matters more than almost anything else.
In my experience, I lost grafted roses when winter hit -15°F (-26°C) without warning. The bud union froze and the named variety died. What grew back the next spring was wild rootstock, not the rose I had planted. That taught me which roses work in my zone.
Trials in Clay County by Minnesota tested rose cold limits. They proved roses can survive -35°F (-37°C) with only mulch and natural snow. These trials used own-root shrub roses bred for cold climates. Your store-bought rose won't match this tough performance.
The roses freeze temperature that causes damage starts lower than you might think. Light frost below 32°F (0°C) won't hurt dormant roses. Damage starts when temps drop to 20°F (-7°C) and stay there. The bud union on grafted roses freezes at about 10-15°F (-12 to -9°C) without protection.
Own-root roses have a survival advantage in cold climates. If the top freezes to the ground, new growth sprouts from living roots in spring. The plant that grows back is still your named variety. Grafted roses can't do this once the bud union freezes.
Choose roses rated for at least one zone colder than where you live. If you garden in zone 5, look for roses hardy to zone 4. This buffer gives your plants wiggle room during harsh winters. Check plant tags or nursery websites for hardiness ratings.
You can protect borderline roses with some simple steps. Pile 8-12 inches of mulch around grafted roses before winter arrives. This insulates the bud union from the coldest temps. Rose cones and burlap wraps add a few more degrees of protection when you need them.
Some damage is normal even on hardy roses after cold winters. Wait until spring growth starts before you assess the damage. Canes that look dead may still sprout from lower buds. Prune dead wood once you can see where new growth begins on your plants.
Read the full article: When to Plant Roses for Beautiful Blooms
