This section is from the book "The Standard Cyclopedia Of Horticulture Vol2", by L. H. Bailey. See also: Western Garden Book: More than 8,000 Plants - The Right Plants for Your Climate - Tips from Western Garden Experts.
The hybrid varieties of Clematis, commonly known as the large-flowering sorts, are, when successfully grown, among the most beautiful of hardy climbing plants. The commercial propagation and growing of most of the large-flowering varieties, however, is attended with so many difficulties and disappointments that it has never been very generally attempted by nurserymen or florists in this country. At the present time there are scarcely half a dozen houses on this continent who attempt the propagation of clematis to any considerable extent, and it is only within the past thirty years that clematises have been commercially grown even by this limited number. Prior to that, practically all of the large-flowering clematises planted in this country were imported from Europe, the major part being supplied by Holland, whose moist atmosphere and black soil produces large, vigorous plants, but whose climatic conditions are so entirely different from those usually found in this country that the plants often failed to adapt themselves to their new surroundings, and did not thrive to the extent that their good size and vigorous condition seemed to give promise.
The propagation of clematis throughout Europe is usually effected by grafting pieces of well-ripened, year-old wood upon roots of almost any of the more vigorous-growing species, Clematis Flammula being most commonly used. In this country, on the contrary, the method commonly pursued is by means of cuttings from young wood, stuck in sand, with gentle bottom heat, usually during May or June. So far as concerns the comparative vigor and desirability of plants produced by these two methods, there is small choice between them. Propagation by cuttings is, in this country, the more rapid and economical way, and further, it removes the possibility, sometimes realized in grafted plants, of sprouts being thrown up from the roots, and, if in the hands of an uninformed amateur, entirely "running out" the variety grafted in; thus considerable annoyance is avoided.
Clematises hybridize so readily that the number of varieties resultant from various crosses forms a long list. But while so many have been dignified with names and places in the catalogues of nurserymen, yet the varieties of large-flowering clematis that have proved so valuable as to secure permanent places for themselves in popular demand can almost be counted upon one's fingers. There are many varieties possessing most beautiful shades and variations of coloring that fail to attain popularity, chiefly on account of deficiency in two essential characteristics-vigorous habit of growth and abundance of bloom. Clematis Jackmanii, purple, originated in 1862, by Mr. George Jackman, was one of the first hybrid clematises introduced, and still stands as the most popular, and, of its color, the most valuable variety yet known. The variety, Madame Edouard Andre, a deep rich crimson, is distinct and novel, being at this time about the best large-flowering sort of a truly crimson shade. It is not quite so vigorous habit as the Jackmanii, but its flowers are similarly massed, though not produced in quite such profusion. Clematis Madame Baron Veillard is a distinct variety.
It is of exceedingly vigorous habit, and the flowers are quite freely produced, though, being more dispersed over the plant, they do not make so much of a show as do varieties whose flowers are closely massed. The flowers are of very large size and of a light rose-color, shaded with lilac. Of white varieties, Henryi, Mrs. George Jackman and Lanuginosa Candida, all of them introduced long ago, still remain about the most desirable ones known. Ramona, deep sky-blue, is a variety which originated some twenty-five years ago. It is of extra-large size, often 9 to 10 inches across, of very vigorous habit and free-flowering.
Of double-flowered varieties, Duchess of Edinburgh, white, is the best known in this country, and about the most desirable. John Gould Veitch is a double sort with flowers of lavender-blue, but has seemed a shy bloomer and of weak habit. Mme. Grange (purplish violet), Star of India (purple), Velutina Purpurea (purple), and Viticella Venosa (reddish purple), are all desirable varieties.
Although they are in reality slightly less hardy than the Florida and Patens types, varieties of the Lanuginosa, Viticella and Jackmanii types,which produce their flowers from young growing wood, are recommended for northern localities. Plants of these types, even if frozen back to the ground, will still produce a good show of flowers, since, as stated, they bloom from the recent vigorous wood, even if the old tops are killed. Indeed, they need to be pruned back considerably anyway to induce a free growth of young vigorous blooming wood. With plants of the Patens and Florida types, however, which blossom from year-old wood, a severe freezing back of the plants would destroy the crop of flowers for the year.
Of the small-flowering varieties, Clematis paniculata (white), introduced from Japan, has proved to be a wonderfully valuable acquisition in this country, and has become exceedingly popular. It is of remarkably vigorous habit, often making a growth of 20 to 25 feet in a season. It seems thus far to be entirely free from disease, is delightfully fragrant, and so floriferous that the blossoms form a dense sheet of bloom, remaining in full beauty for several weeks. The foliage is very thick and heavy, thus making it very desirable for covering porches and arbors.
Crispa (blue) and texensis (red) are species with very pretty, bell-shaped flowers. They are easily grown and do well in almost all situations.
The perennial, non-climbing varieties of clematis are most pleasing border plants, succeeding well in all ordinary soils and making a rich show of bloom at their flowering season. Davidiana (blue) and recta (white) are about the best known and most desirable varieties of this class.
To grow clematis most successfully, they should be given a good depth of loamy soil, with a fair supply of well-rotted manure spaded in and thoroughly distributed through the soil. In hot, dry weather, the plants should be regularly watered in order to obtain the greatest number of flowers possible, for the plants are very susceptible to injury by drought. A point of great importance, especially in caring for newly set plants, is to provide a firm support for them to climb upon. A solid wooden or metal trellis is preferable, for the reason that it prevents the plants from being whipped about by the winds, which often results in breaking the stalks just above the ground or else in cracking the outer bark of the stalks and rendering them more liable to the attacks of insects and fungous diseases. Training the vines upon strings, or a pliable support of any kind, is not to be advised for this reason. Propagation of the hybrid varieties is effected both by cuttings and by grafts. All of the type varieties grow readily from seed.