Clematis is a well-known group of beautiful flowering climbing plants. The clematis group includes evergreen, deciduous, shrublike and herbaceous perennial forms. Today I wish to draw your attention to a couple of native clematis species that deserve better recognition.
The natural distribution of clematis is confined to the Northern Hemisphere. There are estimated to be 295 species in the genus; in Japan alone there are approximately 19 species.
The genus Clematis (senninso) belongs to the buttercup family (kimpoge-ka, Ranunculaceae). The name clematis originates from the Greek klematis, a name which was used for various types of climbing plants. C. florida (no relation to the U.S. state), which is native to China, was introduced to Japan between 1661-73. Many of the common garden clematis that gardeners cultivate today originate from this plant.
Japanese botanists have broken the clematis genus into two easy-to-understand groups. Plants with upward-facing flowers belong to the senninso group and clematis with drooping flowers belong to the hanshozuru group.
C. japonica (hanshozuru), a deciduous climbing shrub, is a typical clematis with drooping flowers. They bloom between May and June, their natural habitat being open spaces on mountains and woodlands. Clematis flowers have no petals; the four showy petal-like structures, red with a thin white margin, are in fact sepals. Botany is full of these little pitfalls. The plant world seems to try hard to confuse humans, and it does a good job!
C. japonica’s leaves are ternate, i.e. a compound leaf divided into three leaflets. Many clematis species have ternate leaves.
C. terniflora (senninso) and C. apiifolia (botanzuru) are two species of summer-flowering clematis. At first glance there seems to be no difference between the two. Both species have white flowers and bloom at the same time, August to September.
A distinguishing point between the two species is the shape of the leaves. In C. terniflora the leaves are pinnate and each compound leaf has three to seven oval, smooth-edged leaflets. (In botany, if the edge of a leaf has no teeth, it is known as “entire,” zen’en.)
C. apiifolia, on the other hand, has ternate leaves, and its long, oval leaflets are deeply toothed. Its natural range is in temperate to warm-temperate areas.
C. terniflora is distributed throughout Japan, Taiwan, the Korean Peninsula and China. The English name is “sweet autumn clematis,” because it has flowers which are slightly fragrant. Its natural range is temperate to semitropical. The plants grow close to the roadside or at the edge of woodlands, always in a sunny position. A semi-woody climber, its main stem repeatedly divides into a much-branched climbing shrub. The petioles wrap themselves around stems of shrubs and wild perennials.
The dry seed of the clematis is attached to a 3-cm-long feathery style, from which it gets its Japanese popular name: “Sennin” means “hermit,” and the long feathery style is thought to look like a hermit’s beard. In fact, in Europe also the species Clematis vitalba is known as “old man’s beard.”
As with many Japanese plants there are closely related species and natural geographical varieties. Both C. terniflora and C. apiifolia have close relatives. One is C. apiifolia var. bitnerata, known as me-botanzuru or ko-botanzuru. Its natural range is from the Kanto to the Chugoku region in Honshu. The seed has no hair; leaves often show double or triple sets of small ternate leaflets.
C. uncinata var. ovatifolia is known in Japanese as Kii sennin-so. This semievergreen climber closely resembles C. terniflora, but is native only to the Kii Peninsula south of Osaka and Kumamoto in Kyushu. Its leaves are leathery and doubly ternate, with entire margins. Its flowers are in panicles.
Both C. terniflora and C. apiifolia are good screen plants. When they have finished flowering, prune the year’s growth back to one or two buds. This operation can also be done in early spring.
Clematis will grow better if its roots are shaded from direct sun, so one should spread bark or other mulch around the base of the young plant. The upper part of the plant, however, should receive full sun.
Clematis requires regular watering. A humus-rich soil that is free draining but can also retain moisture is best. Both species, being climbers, should be planted next to a trellis, or tree trunk where they can freely grow.
These clematis species may not be sold in every garden center, but if you don’t see them, ask to order them.