In 1860 some plants were raised in the nursery of Messrs Jackman at Woking from seed of C. lanuginosa pollinated by C. viticella ‘Atrorubens’ and C. × eriostemon ‘Hendersonii’. This batch flowered in 1862, and from it two forms were selected and put into commerce – one as C. jackmanii and the other as C. rubro-violacea. Since two pollen parents were used in making the cross, the precise parentage of the former, which is the type of the group C. × jackmanii, is not known for certain, but it is reasonable to assume that it is straight C. lanuginosa × viticella. It is still a valued garden plant today, with flowers 4 to 5 in. across, of a rich, velvety violet-purple.
The importance of the Jackmanii cross (a similar cross was made on the continent at about the same time) was that it united the genes of the European C. viticella with those of one of its E. Asiatic allies. The contribution of this species was: deepness of flower-colouring and the habit of flowering entirely on the season’s growths as the days shorten. The Jackmanii group of hybrids is, however, a complex race in the formation of which the other E. Asiatic species may have played a part and thus extends beyond the boundaries of C. × jackmanii. The hybrids of this group commence to flower in June or July and some are still gay in October if the weather remains open and sunny. They may be pruned to within a foot of the older stems each spring, being for the most part vigorous growers, and flowering on the shoots of the current year.
cv. ‘Superba’. – Similar to the original C. × jackmanii but with broader sepals of a more reddish purple, rich maroon when the flowers first expand. A very vigorous and beautiful clematis. It is of interest that ‘Madame Grangé’, raised in France before 1877, and bearing some resemblance to ‘Superba’, is known to have been a direct cross between C. lanuginosa and C. viticella. This cross was also made by the French nursery firm of Simon-Louis in 1861 and named by them C. splendida. The plants from this cross were said to resemble C. × jackmanii very closely, but the example figured in Revue Horticole, 1865, p. 70, has flowers of a redder purple.