The Clematis genus consists of many species grown for their flowers. Most Clematis species are deciduous, vining perennials. White clematis are particularly striking in the landscape; their pure, bright blooms contrasting with their green foliage. Determining the best white clematis for your garden depends on the type of flower and bloom season you prefer, as well as the growing conditions where you live. In addition, most Clematis species are imports to the United States, so gardeners need to avoid those that may be exotic, invasive species.
Gardeners interested in growing native plants have several white-flowered clematis from which to choose. Aggie-Horticulture recommends the western white clematis, C. ligusticifolia. An eastern native, often called virgin’s bower, is C. virginiana. Both have small white flowers and exhibit better behavior than the similar-looking, but exotic, often-invasive sweet autumn clematis (C. paniculata or C. terniflora) and old man’s beard (C. vitalba). Both natives bloom profusely, grow enthusiastically and can benefit from being cut back almost to the ground.
Some of the earliest-flowering clematis varieties, which bloom on old wood, have beautiful white flowers. Among the best, according to Clemson Cooperative Extension, are C. armandii, and C. montana, which both produce showy masses of small blooms in the spring. C. montana var. grandiflora, with somewhat larger flowers, received a Royal Horticultural Society Award of Garden Merit. These varieties will not re-bloom and need summer pruning to assure they generate new growth that will have time to mature for the next spring’s bloom.
Large-flowering clematis may bloom on both old and new growth. They are darlings of the summer perennial garden. Their white blooms are particularly visible, with all varieties’ flowers spanning at least several inches. These clematis types can provide interest grown through trees and shrubs that bloomed earlier. Two hybrids, Henryi and Marie Boisselot, which received the RHS AGM, are readily available to U.S. gardeners. Clemson also recommends C. lanuginosa Candida for blooms up to 9 inches across, and C. florida for warmer parts of the United States. Prune these clematis types lightly in late winter for best bloom.
Late-flowering clematis bloom only on new wood. Some of the best whites, according to the Iowa State University Extension, include C. recta and C. x jackmanni Alba. Clemson recommends C. viticella Alba Luxurians, which is another RHS AGM winner. To assure that you have these season extenders in full bloom well into the fall, be sure to prune them back in late winter.