Rugosa roses, Explorer climbers, and own-root shrub roses such as Knock Out come through Pennsylvania winters with little help. Hybrid teas, tree roses, and most grafted roses sold in spring need a mound of soil or a sheltered spot to survive, and in the colder counties even that may fall short. The type of rose matters at least as much as summer care in deciding the outcome. Here is how to sort survivors from casualties before you spend the money.
Which roses survive a Pennsylvania winter
Pennsylvania spans USDA hardiness zones 5a to 7b, according to the USDA Plant Hardiness Zone Map. That system rests on a single number, the average annual extreme minimum temperature. It tells you how cold the worst night of a typical winter gets and says nothing about wind, snow cover, or summer heat. Philadelphia sits at the mild end of the range. The northern tier and the Alleghenies sit at the cold end.
Which types clear zone 5a without help?
Rugosa roses and their hybrids are the workhorses of the cold counties. So are the Explorer roses, a series bred in Canada to take prairie winters. Species roses and many once-blooming old shrubs belong in the same group. Most modern landscape shrub roses, the Knock Out family among them, also get through. They often lose some cane tips and leaf out from lower down in spring, and they are back to full size by midsummer.
Hybrid teas, floribundas, and grandifloras are the ones that need help. In zone 5 and the colder edges of zone 6, they usually die back hard in a normal winter. In a severe one, they die to the ground and take the grafted variety with them. In zone 7, which includes Philadelphia, a mound of soil over the crown gets most of them through. The methods for that live on the page about winter protection for roses.
How do Pennsylvania frost dates affect roses?
Cold hardiness is only half the story. At the Philadelphia reference station, the NOAA NCEI U.S. Climate Normals for 1991-2020 put the last spring 32°F freeze between March 29 and April 6. The first fall freeze lands between November 5 and November 16. Both are ranges built from the 30 to 70 percent probability band, so any single year can fall outside them.
Philadelphia is the mildest corner of the state. The northern tier and the Alleghenies run several weeks later in spring. A rose that leafs out during a warm March gets its soft new shoots burned by the next hard freeze. A rose still pushing growth in early November goes into winter with unripened wood. Rugosas and Explorers shut down early and wake late, which is a large part of why they win in the cold counties.
Named roses that hold up here
The cultivars below are widely sold, easy to find at nurseries and by mail, and have a long record in the Northeast and Midwest. They are listed by what they handle, because a name on a tag means little until you know what it survives.
| Cultivar | Type | What it handles |
|---|---|---|
| Knock Out | Repeat-blooming shrub | Zone 5 winters with some tip dieback, strong against black spot |
| Therese Bugnet | Hybrid rugosa | Northern tier and Allegheny cold, wind, and heavy snow |
| Hansa | Rugosa | Cold, road salt, wind, and thin soil |
| New Dawn | Repeat-blooming climber | Typical winters across the state, with occasional tip dieback in the coldest counties |
| William Baffin | Explorer climber | The coldest spots in the state without protection |
Which shrub roses are the easiest to keep alive?
Knock Out is the default for a reason. It blooms from late spring until frost, resists black spot well, and does not need deadheading. In a hard winter the canes may blacken, and the temptation is to cut them all out in March. Resist it, and wait for buds to swell before pruning, because the plant often regrows from live wood well above the ground. One caution applies to the whole Knock Out family. Rose rosette disease, spread by a tiny mite, has hit these plantings across the eastern half of the country, and the rose diseases in Pennsylvania page covers what to watch for.
Therese Bugnet and Hansa are the answer for anyone gardening in the snow belt or in the colder parts of the territory. Therese Bugnet is a tall, upright hybrid rugosa with fragrant pink flowers and reddish canes that look good in winter. Hansa is a dense, thorny rugosa with double magenta-purple flowers, a strong clove scent, and big orange hips in fall. It tolerates the salt spray along a plowed road, which few roses do.
Is there a climber that survives here?
New Dawn is the old reliable, a pale pink climber that flowers repeatedly through the summer. In zone 5 you may need to tie the canes loosely and accept some tip loss. For the harshest sites, William Baffin and John Cabot from the Explorer series carry cold tolerance that New Dawn cannot match. They bloom in a heavier flush earlier in the season and then trail off.
Sold here, but not for this zone
Garden centers and big-box stores stock roses on a national schedule. A pallet of plants that sells well in Georgia or California shows up on a Pennsylvania shelf in the same week, with a tag that may or may not mention the cold. A lot of what sits in the rose aisle is marginal here, and some of it will not come through a zone 5 or 6 winter without real work.
Which roses on the shelf need winter help?
Hybrid teas lead the list. Classics such as Peace and Mister Lincoln are sold everywhere, and both are grafted plants that struggle in the colder counties. Tree roses, which are grafted on a tall trunk with the variety on top, are among the most exposed, because the whole head sits above the snow. Many English roses in containers do well in zone 7 but lose canes in zone 5 or 6. Tea, China, Noisette, and Bourbon types sold by mail were bred for warmer ground and rarely last in the northern tier. Boxed grafted roses sold in waxed canes at hardware stores in late winter fall into the same group.
None of these is banned. A hybrid tea in southeastern Pennsylvania is a fair bet if you are willing to do the work, and mound soil over the graft union before the ground freezes, or the variety above it is the first thing lost. Tree roses need the whole plant tipped over and buried or wrapped, which is more effort than most people expect when they carry one to the register.
What to check on the label before buying
Three things on the plant tell you more than the photo on the tag: the grade, whether it is own-root or grafted, and the zone rating. Roses are sold in grades, with the highest grade being the thickest, best-developed plant. Buy Grade 1 when you can, because a stronger plant has more stored energy to rebuild after a hard winter. A Grade 2 bare-root bush is cheaper for a reason.
Is the rose own-root or grafted?
A grafted rose is a variety joined to a different, tougher rootstock. The joint shows up as a swollen knob at the base of the canes. An own-root rose grows on its own roots all the way up. The difference barely matters in a mild climate, but it matters a great deal as the winters get colder. If the canes of a grafted rose freeze to the ground, whatever regrows comes from the rootstock, and it is usually a different, less showy rose. If an own-root rose freezes back, it regrows true to the name on the tag.
That is why choose the own-root plant when the tag offers both. Many mail-order nurseries label their plants clearly, and some sell only own-root roses. At a store, look for the words “own root” on the tag or check the base of the plant for the knob. A zone rating on the tag is the grower’s national estimate, so match it to the hardiness zone of your own address, which may differ from the figure for your county as a whole.
Checking this against your own county
The zone range for the state covers a lot of ground, and a valley in Tioga County does not behave like a south-facing slope in Chester County. Penn State Extension has an office in every county, and the staff there know the local cold pockets and which roses fail in their area. Before you order, ask the county office which zone your address falls in. For the basics of siting and care once you have chosen, see growing roses in Pennsylvania.
Common questions
Do Knock Out roses need winter protection in Pennsylvania?
Usually not. In the colder counties the canes may blacken and die back in a hard winter, and the plant still regrows. A light mulch over the base helps in zone 5, but heavy mounding is unnecessary.
Are hybrid teas worth growing in Pennsylvania?
They are worth it in zone 7 and the milder parts of zone 6, if you will mound soil over the crown each fall. In zone 5 and the northern tier, a rugosa or shrub rose is usually the easier, more reliable choice.
How can I tell whether a rose I already own is grafted?
Look at the base of the plant, just above the soil line. A knobby swelling where the canes emerge marks the graft. If the canes come straight from the roots with no knob, the plant is likely own-root. Nursery records or the original tag are the surest check.
What is the hardiest rose for the Allegheny Plateau and the northern tier?
Rugosas such as Hansa and Therese Bugnet, along with Explorer roses such as William Baffin, are the strongest picks. They handle the deepest cold and the longest winters, and their late spring waking makes them less vulnerable to a hard freeze after leaf-out.