This section is from the book "The Florists' Manual", by William Scott. Also available from Amazon: The Florist's Manual.
Although more properly belonging to the nurseryman than the florist we are continually asked to supply plants of several varieties and species of these free flowering hardy climbers.
Some of the species are readily increased by cuttings. The paniculata type root freely from pieces of the young growth and there is no better place than the gentle heat of a hotbed. They all are, however, bought very cheaply from the nurseryman. The large flowered Jackmanii type are usually grafted on the roots of C. flammula, the common European, or the root of any strong growing variety. The florist buys his clematis and is more interested in knowing how to make them grow satisfactorily than how to propagate them. Very strong plants of Jackmanii and other large flowering varieties are imported every fall, arriving here early in November or perhaps a little earlier. They have usually a good growth with a great bunch of roots. Thousands of these are sold and thousands die, and provokingly after living one or two or more years.
We spread out the roots and Jay them in trenches in the coldframe during winter and in severe weather cover with glass, removing it before they get anyway forced by the suns of March. We believe they are more satisfactory to our customers planted this way than potted and given any time in the greenhouse. The potted plants look well when sold, but are more liable to suffer from neglect after planting. In very strong plants there is such a mass of roots that it is impossible to spread them sufficiently for all to get some earth around them, so we cut out about half the roots, which enables us to get some soil among them. You dare not guarantee the clematis. If you do you will have to make good your losses on some other article. But you can plant them with care and give good advice as to the attention they need. They are nearly always planted against a veranda, whose overhanging roof often keeps the rain away, or they may be on the side of the house or an aspect from which the prevailing rains are infrequent. They should during summer receive copious waterings. When planting out each clematis should receive a barrow-load of good, rich soil and not be put into a small hole and have clay or brickbats to feed on, which is often the result of the grading and sodding that is done around a pretty house.
In milder countries the gorgeous Jack-manii and its kindred varieties may retain their stems through the winter; with us they do not, but when well established the roots have such vigor that the young shoots spring from the ground in a very few weeks, and by end of June are a gorgeous mass of bloom seven, eight and nine feet high, and five or six feet across. All these flower from the growth of the same year.
Plants of Jackmanii, Henryii or any of that type make splendid decorative plants grown on a balloon or flat trellis in large pots. For this purpose they should not be cut down, as the frost does our outside ones, but wintered in some cool house and merely thinnned out and tied in spring before starting into heat.
There are a great number of species and some of them are very distinct. A few of them are natives of North America and make splendid plants for covering fences, railings, etc.
C. paniculata is very hardy and is covered from July on with its white, finely divided flowers, resembling almost balls of cotton.
C. coccinea is a very distinct species with yellow and vermilion flowers of an odd shape; fine for verandas.
C. flammula has white flowers, is very hardy and one of the strongest growers.
C. Fortunei, small, white fragrant; fine hardy climber.
C. Virginiana, a very strong growing climber with small white fragrant flowers.
The five species last mentioned do not require any special care, and when once established live for years. It is what is known as the Jackmanii type, one of the first hybrids of which has immortalized the name of the raiser, Mr. Jackman, of Surrey, England, that need the best of attention in planting, etc., and which are to many people the only clematis. An old species from China with pale lavender flowers five or six inches in diameter must be one of the parents of Jackmanii. Of this beautiful type there are a number of varieties, and among the best are:
Jackmanii, still one of the very best color; a rich purple.
Jackmanii superba, violet purple.
Star of India, reddish plum color.
Henryii, the best white; very large.
Mme. Edouard Andre, a very distinct variety, approaching a bright red.
Miss Bateman, an attractive variety; white flowers with dark anthers; medium flower, dense grower and free bloomer, but not continuous.