Cold hardiness is a messy concept. Nursery catalogs would have you believe it’s as simple as a number, namely, your hardiness zone number, which the US Department of Agriculture assigns to a given location based on its average minimum winter temperature. So for instance, when a catalog claims a certain rose is suitable for zones 6 to 9, it is saying the plant will thrive anywhere from, say, Connecticut to northern Florida. There’s a problem with this system, however: A plant’s ability to survive winter and thrive the following season depends on a lot more than just minimum winter temperatures. Some roses tolerate sub-zero temperatures just fine, only to be fooled out of their dormancies during a thaw, causing substantial damage when freezing weather inevitably returns. Then there are horticultural factors that affect cold hardiness: Was the plant already stressed going into winter? Is it positioned in a protected location or an exposed one? How wet or windy is the site?
Another problem with hardiness zone recommendations is that they don’t account for how climate affects a plant’s growth habit. In our garden we have several so-called “climbing” roses that easily survive the Connecticut winter but die back close to the ground most years. As a result, these climbers don’t climb. Perhaps “shrub” might be a better name for them, at least in our garden.
Which brings me to the main subject of this post: the “surprise” climbers of 2020. We had a mild winter this year. The temperature never dipped below 5° F (-15° C). We experienced a January thaw, but it wasn’t enough to stir the roses from dormancy. We did have some later spring freezes, though none so severe as to damage established plants. So as I begin my fourth season at the park I’m finally meeting some climbers for the first time. Many that usually get whacked to the ground in winter now spread their canes luxuriously over our fence lines, rewarding us with their unusual blooms.
- A “surprise” climber in 2020, most likely ‘Mrs. Arthur Curtis James,’ a Brownell rose from the 1930s
One of my favorite borderline-hardy climbers is ‘Zépherine Drouhin.’ Catalogs will tell you this cultivar is hardy to zone 6, even chilly zone 5. We’re in zone 6, and true enough, Zépherine does survive in our park. We grow four specimens–three in different spots along a fence and one in our heritage rose garden. But the catalogs also tell you that ‘Zépherine Drouhin’ can soar to heights of over 15 feet. Sure, I’ve seen photos of specimens swallowing French manor walls or enveloping bucolic southern arbors. But in our garden, Zépherine typically forms a low, tidy shrub. That is until this year: We’ve finally managed to get its canes to cover portions of our fencelines. (Full disclosure: The roses in our garden are fully exposed without any barriers to protect them. Just down the road from the park, our executive director has successfully trained ‘Zépherine Drouhin’ past her first story against a southeast-facing wall). This season, as ‘Zépherine Drouhin’ realizes its height potential in the park, the public can enjoy its fragrant blossoms right at nose height. And, pardon my subjectivity, but its fragrance is not only stronger, but better than that of many roses.
- ‘Zépherine Drouhin’: If only I could photograph fragrance
‘Zépherine Drouhin’ belongs to a class of roses known as the “Bourbons,” named for the Isle de Bourbon (now Réunion) in the Indian Ocean where they were first hybridized. A grower by the name of Bizot brought the rose to France around 1870 (plus or minus a few years), calling it ‘Zépherine Drouhin’ after the wife of a contemporary horticulturist. Prized for its thornless canes and fragrant, double pink blossoms, the cultivar soon gained popularity throughout Europe. Some sources claim Zépherine blooms from Spring straight through first frost, but at Elizabeth Park we see just one big flush in early to mid-June followed by occasional scattered blooms over the summer and fall.
- ‘Zépherine Drouhin’ in the Heritage Rose Garden
Here’s some other surprise climbers in 2020:
- ‘Easlea’s Golden Rambler’: another borderline-hardy climber
- Anyone know the name of this loud, orange-pink climber?
Scanniello, S. (1994). Climbing Roses. Upper Saddle River, NJ: Prentice Hall