Our growing season is coming to a close, and this summer we have seen many beautiful modern roses at the nurseries. These recently introduced roses possess characteristics of cold hardiness, disease resistance, and recurrent summer bloom that echo from their ancestors of millions of years ago. Roses are among the most ancient of plants. A thirty-five million years old fossil of a rose was found in North America. Roses originated in Asia about 70 million years ago.
These ancient original wild roses are called species roses. Their legacy of cold hardiness, disease resistance and recurrent bloom has provided a foundation that has enabled hybridizers, in especially the last 200 years, to develop rose varieties that are not only cold hardy, but also disease resistant, and also possessing recurrent or continual bloom within each plant.
Most of the species roses were winter tender, not surviving in climates colder than Zone 7. (Here in Flagstaff we live in a colder zone, Zone 5.) However, Rosa arkansana and Rosa canina were cold hardy.
Rose diseases such as the black spot fungus and powdery mildew fungus have always been serious problems for roses. Black spot infection prevents the leaf from photosynthesizing; the leaves die and fall off. Severe powdery mildew prevents rose buds from opening, so the rose cannot reproduce. Several of the ancient wild roses in Asia were disease resistant, such as Rosa dividii, which was resistant to black spot.
Most of the species roses were covered with a short flowering of small five-petaled, white or pink blooms in the spring. The species rose from China Rosa chinensis, however, bloomed a second time, in late summer. Its welcome introduction into Europe in the 1700s and 1800s and then into North America ignited an intense experimentation to integrate these superior traits into known roses. Rose hybridization is a huge business all around the world. Families for generations and companies years old have honed hybridization into a complex science. It takes about 10 years to bring a promising rose to market.
In the hospice garden most of the roses are not only cold hardy, but also disease resistant, and recurrent or continual blooming. Some of the best are our Flower Carpet groundcover roses, cold hardy to Zone 5 and covered with clusters of blooms until late fall; ‘The Fairy’ polyantha (a small shrub), is cold hardy to Zone 4, and the ‘John Cabot’ climber, is cold hardy to Zone 3.
The DNA that existed in the very first roses from millions of years ago is still present in the old garden roses of the last six hundred years and in the modern roses developed since the first modern rose in 1867. So next spring when you shop for roses, take a minute to marvel at the timeless heritage of the rose, and the work and care of generations of hybridizers who have brought us the incredibly vigorous and carefree roses of today.