New rose classes are not created without a reason. There have been a slew of roses that people and the hybridizers claim are different and deserve a new rose classification,and correctly were not given one,including Pernetianas,Lambertianas,Brownell Hardy Hybrid Teas,Buck Roses,Explorer Roses,and Austin Roses. The problems were more of trying to define the class and many were short lived.
In the 1950s,they made an exception for a unique rose,Rosa kordesii. This 1940 cross was introduced in 1952. Wilhelm Kordes in his book,Roses,claimed that he succeeded in obtaining a self pollination of ‘Max Graff’,a Rosa rugosa,and a Rosa wichuraiana hybrid. He stated that it combined the hardiness of R. rugosa with the large flowers of garden roses. Normally this cross would result in a sterile triploid rose. However,nature he claims,departed from the normal and this rose was a polypoid and ended up with 28 chromosomes. By using R. kordesii in his breeding program,Wilhelm hoped to produce climbers with recurrent bloom,bright colors,strong growth,and clean foliage. In Modern Roses 10,it is stated that R. kordesii is “a new species that arose in culture as a result of a spontaneous chromosome doubling in a Rosa rugosa x Rosa wichuraiana hybrid”. The blooms are “deep pink,semi-double,cupped shaped,foliage shining green,fruit elliptic-ovoid with 28 chromosomes”.
I personally don’t think Rosa kordesii itself made much of an impact,and it is difficult to find a nursery that sells it,however,it has proved to be invaluable in breeding programs. With its shiny,disease resistant foliage and winter hardiness,Rosa kordesii was to pass on these characteristics to its offspring. All of the offspring of Rosa kordesii are classified as kordesii (ARS designation K),a ‘classic’shrub class. Members of this class are eligible for the Best Classic Shrub certificate at ARS shows.
Modern Roses 10 lists 32 kordesii. Most of the breeding took place between 1954 and 1966. There were no new introductions until the Explorer and hardy roses started to appear in the late 1970′s. Most of the kordesii are either red or deep pink,however there is a white,‘Ilse Krohn Superior’,and a medium yellow,‘Soeur Kristin’. Modern Roses 10 also lists 6 other non-kordesii classed roses with R. kordesii in their bloodlines,such as ‘Frontenac’and ‘Aurora’.
Some of the Best Kordesii
‘Dortmund’(1955) is one of the first and best roses coming from R. kordesii. It is a cross with R. kordesii and a seedling. This rose is known for its shiny disease resistant foliage and single-petaled,bright red blooms with a white eye. The large clusters are very impressive and can win at the show,plus the foliage is so clean and shiny,it is often used in arrangements. ‘Dortmund’can be a large shrub or a climber. It has good recurrent bloom. Two other early kordesii roses are the medium red ‘Hamburger Phoenix’and the light yellow ‘Leverkusen’(both 1954).
In Southern California ‘Parkdirektor Riggers’,‘Karlsruche’and its seedling,‘Rosarium Uetersen’do very well,along with two of my personal favorites,the red ‘Heidelberg’(1959) and ‘Sympathize’(1964). I was impressed by the ‘Heidelberg’grown as a pillar rose in Washington Park,Portland,Oregon,and by the large specimen of ‘Sympathize’at Descanso Gardens in La Canada,California.
Rosa kordesii was used widely to produce winter hardy roses. The Explorer series of roses have a lot of kordesii bloodlines. This includes the pinks ‘John Davis’,‘Louis Jolliet’,and ‘William Baffin’(both Rosa kordesii seedlings),and the reds ‘Champlain’(a complex R. kordesii and R. spinossisima cross),‘Henry Kelsey’,and ‘John Cabot’. Explorer Roses tend to do well in our climate,but would prefer the protected or semi-shade areas of our yards.
Other Breeding Programs
Dortmund has been used in other breeding programs,most notably by Ralph Moore in his creation of the miniature roses –‘Sincerely Yours’,‘Rose Gilardi’,‘Scarlet Moss’,and ‘Chick-a-dee’.
So if you want a clean,vigorous climber,mini,or shrub rose;consider one of the kordesii.
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