Rosa rugosa Thunb.

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'Alba'

Flowers blush in bud, opening pure white, single. Vigorous and free-fruiting. The origin of this form is uncertain; it may descend from the white-flowered seedling raised by the nurseryman Ware of Tottenham early in the 1870s.

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R 'Calocarpa'

A handsome rose with branches less thick than in R. rugosa, clusters of bright red fragrant flowers borne over a long period, followed by globose, scarlet fruits {3/4} in. wide, crowned with the sepals. Raised by Bruant of Poitiers and sent out about 1891. A hybrid of R. rugosa crossed with “R. indica”, possibly some form of Crimson China. It was stated by the raiser to come true from seed, a statement of very doubtful validity (R. rugosa calocarpa André; R. × calocarpa Bak. in Willmott).

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R 'Hollandica'

A hybrid of R. rugosa, much used as a stock for garden roses, especially standards. It is a suckering shrub with mauvish pink, almost single flowers, of no value as an ornamental, though often seen in neglected gardens. It flowers from summer to autumn.

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R × iwara Sieb. ex Reg.

A natural hybrid between R. rugosa and R. multiflora, occurring occasionally in the wild. Of spreading habit, intermediate between the parents. The introduced form (as R. yesoensis) had small white flowers and could be described as two beautiful species spoilt.

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R × jacksonii Baker in Willmott,

This cross was made at the Arnold Arboretum by Jackson Dawson, towards the end of the 19th century. Here belong ‘Lady Duncan’, named by Dawson, and ‘Max Graf’, of independent origin (see further on p. 190 and also R. kordesii below).

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R kordesii H. D. Wulff

This rose, raised by the famous German breeder Wilhelm Kordes, is an interesting example – one of many now known – of how what is in effect a new species can arise in cultivation as a result of hybridisation followed by a doubling of the number of chromosomes. The parent of R. kordesii is ‘Max Graf, a very vigorous and hardy hybrid between R. rugosa and, probably, R. wichuraiana, both diploid. Herr Kordes acquired a plant as soon as ‘Max Graf was put into commerce in 1919 and, seeing its potentialities as a parent, attempted to breed from it. But, like most hybrids of R. rugosa, it proved to be sterile both in crossing and when selfed. However, two fruits were eventually obtained, from which two seedlings were raised. One of these proved to be completely fertile and was found, on cytological examination, to be tetraploid. This was named R. Kordesii in 1951. Using R. kordesii as a parent, Herr Kordes raised a group of repeat-flowering climbers with glossy, disease-resistant foliage, of which several are described in the second section (W. Kordes, in The Rose Annual 1965, pp. 99–102).

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R × micrugosa Henkel

One of the best primary crosses, being intermediate in habit and foliage, and having large, single, pale pink flowers 4 or 5 in. across. The fruits are greenish and bristly. It was found as a self-sown seedling in the garden of the Strasbourg Botanical Institute and described by Henri de Vilmorin in Revue Horticole 1905, p. 144. From the original hybrid Dr Hurst raised R. × micrugosa ‘Alba’ with white, fragrant flowers borne over a long period. The growth is more erect, and the foliage lighter green.

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R × paulii Rehd.

See ‘Paulii’, p. 194.

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var. ventenatiana C. A. Meyer

This differs from typical R. rugosa in having the stipular (nodal) prickles distinct from the more scattered bristly ones, in the leaves being more obovate and rounded at the apex, and in the smaller fruits. It is a distinct race, confined to S. Kamchatka, and is considered by some authorities to be a natural hybrid between R. rugosa, which is found on the peninsula, and R. amblyotis, a close relative of R. majalis. It was described in 1800 from a plant cultivated by the French nurseryman Cels, and was probably introduced around 1770 though by what means is not known. Since R. rugosa itself also grows on Kamchatka it is possible that the first introduction of the species, known as R. ferox, came at the same time.