I never thought I would see the day in a Zone 3 urban climate when hundreds of ‘Hansa’ shrubs have been devastated from winter killing. Shrubs grown for many years without any winter damage are dead to the ground level. In some cases, the odd cane has survived on large shrubs. I can only conclude that a warm spell in mid-winter followed by -30 C temperatures caused the damage. Several years of drought in the northern Great Plains may also have been a factor. Yet there is no damage to ‘Therese Bugnet’ shrubs. The difference (I can only speculate) is that ‘Therese Bugnet’ has a native species (likely Rosa woodsii) in the parentage and a gene that prevents “waking up” of the shrub during periods of mild weather during the winter.
The experience of ‘Hansa’ being severely winter killed in a Zone 3 climate reminds me of the importance of injecting species into breeding programs, whether it is for cold hardiness, drought tolerance, tolerance of high temperatures or disease resistance. There should be a re-doubling of efforts in this respect, for we do not know how present and future climate changes will affect rose growing. For future successful rose growing, I think that it is essential a wide variety of rose types are developed and this can only be done by developing breeding lines with unused or rarely used species. When one considers that there are over 100 rose species, the potential to develop roses adaptable to a wide range of climates is enormous.
Let’s understand that because we have had such a myopic view of developing roses by not using more species and have allowed big business and the nursery trade to tell us what kind of roses are appropriate to grow and breed, we will only have ourselves to blame when it becomes too difficult in some regions to grow roses.