RHA Newsletter 6(2): 17-18 (Summer 1975)
Outstanding Roses
William J. Radler, Greendale, Wisconsin

In my connection with a botanical garden having a rose garden of over 3,000 roses of approximately 350 cultivars, I have observed some noticeably consistent traits that might be of use in a breeding program. Many of these traits (such as hardiness) are listed in a bulletin that we publish yearly which might be of interest to REIA members. The bulletin is "The Boerner Botanical Garden's List of Outstanding Roses" and can be obtained by writing to the gardens at 5879 S. 92nd Street, Hales Corners, Wisconsin 53130 and enclosing a large, self-addressed, stamped envelope.

One of the consistently outstanding roses since the opening of the gardens in the early 1940's has been 'Soeur Therese,' a yellow hybrid tea of exceptional winter hardiness and vigor. The flower itself has few petals and opens fast, but no other yellow rose has this much vigor and hardiness. Consider the possibilities if 'Soeur Therese' were crossed with roses that transfer good form, ample petalage, and slow-opening qualities.

Another consistently outstanding rose for many years has been 'Golden Jubilee,' a floriferous yellow floribunda. It seems to be of average hardiness with protection in this area, but its claim to fame might be that from our experience it has been completely resistant to spider mites. Since it has never been bothered by this pest, it comes back vigorously each year unlike other varieties of floribundas that are especially loved by spider mites. I have a suspicion that this rose might not make a very fertile parent. If this is true, perhaps the chromosomes could be doubled by the drug colchicine? Is anyone else interested in a spider mite free class of roses?

The worst rose problem next to spider mites in this area is blackspot. Once it is noticed in a garden, it is difficult if not impossible to control. All of the modem roses are very susceptible to the disease, in fact the Autumn Damasks and the Teas and the Chinas are all highly susceptible, and these all had much to do with the origin of modern roses. It is difficult to understand why the professional hybridists have not made a more serious attempt to breed blackspot resistant roses.

In the shrub rose collection at the botanical gardens I have observed blackspot resistance that might be used in hybridizing. While this would be a difficult trait to transfer to modem roses, I'm sure that it is possible. Roses that have exhibited blackspot resistance in our collection include 'Agnes,'* Rosa Gallica Officinalis, 'Versicolor,' 'Therese Bugnet,' 'Lillian Gibson,'* 'Frau Dagmar Hartopp (Hastrup),'* 'Hansa,'* Rosa Eglanteria,* 'Eddie's Crimson,'* 'Konigin Von Danemark,'* and 'Cardinal de Richelieu.' The roses starred (*) also have shown resistance to mildew. 'Agnes' and 'Eddie's Crimson' do not set seed.

From observance of the Hybrid Rugosas, Albas, and Gallicas, I assume that blackspot resistance is transferred as a blended trait. In other words, if a resistant rose is crossed with a susceptible rose, the resulting progeny most likely will be intermediate between the parents. If this is the case, then it would be best to have the resistance factor coming from both parents. If space is a problem, consider the possibilities of producing a race of blackspot resistant miniature roses.