Kentucky Wisteria – Wisteria macrostachya

Kentucky Wisteria – Wisteria macrostachya
Family: Fabaceae (Leguminosae)

USDA Hardiness Zone: 3. Seeds and pods of the Wisteria are reported toxic to humans.

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Kentucky Wisteria climbing on pergola

Kentucky Wisteria is a woody deciduous vine native to in the southeastern United States. It is very similar to the American Wisteria (Wisteria frutescens). Kentucky Wisteria bears unscented bluish-purple flowers in racemes 15-30 cm long (figure 1), a generally average length for the Wisteria family. It produces these flowers after growing only two to three years, making it the quickest wisteria to bloom. Otherwise, its soil and light requirements, behavior, and characteristics are identical to the American Wisteria.

The wisteria are vigorous twining vines that grow to 25 or 30 feet. These vines are most valued for their long, pendant clusters of violet-blue flowers. Varieties are available that produce flowers of varying colors (from white to pink to deep reddish and bluish-violet). Beanlike velvety pods remain after the leaves fall but are not particularly ornamental. All wisterias will bloom, but some vines take as long as 7 to 15 years to produce their first flowers.

Wisteria climbing vine
Figure 3. Wisteria is a Twining Vine

The following practices may help induce flowering: An application of super phosphate in early spring, Severe pruning of the new growth in late spring or early summer, Root pruning by cutting some of the roots with a spade a few feet from the trunk in late fall. Grafted plants or plants that have flowered in the nursery are recommended.

Wisterias are excellent for training on stoutly constructed arbors and pergolas (figure 2). They are best when trained horizontally on a wire or structure 10 to 20 feet above the ground. The vines are excellent for use on open-structured roofs over patios and terraces. Do not plant too closely to trees or shrubs as it will choke them out.

Wisterias sometimes are grown as standards or trees. The plant must be staked in an upright position with the branches removed 4 to 5 feet up the stem and the top pruned heavily. A vigorous, flowering vine may be maintained by pruning back long branches to within five buds from their point of origin in early summer. Repeat this pruning in late summer on new shoots that develop. Remove all thin and weak growth immediately after flowering or in late winter. Wisterias prefer a deep, rich, moist, well-drained soil high in organic matter. A sunny location will favor maximum flower production.

Kentucky Wisteria Flowers

Vines serve many useful landscaping purposes. Where space is limited, vines may be used as dividers or barriers. They can screen unsightly views or provide privacy for the patio or porch. The monotony of a long fence or blank wall may be broken with vines. They can soften harsh structural lines and blend the structure with other plantings. On steep banks and in other areas where grass is difficult to establish and maintain, vines may be used as groundcovers.

Selection of a suitable vine depends on its intended use, location, soil adaptability and type of support. Dense, coarse foliage is desirable if a screen is needed. A fine-textured, slow-growing vine should be selected to add pattern and interest to a stone or brick wall. A decorative vine should possess desirable flowers, fruit or foliage for seasonal interest. Vines are of three different types according to their method of climbing whether by tendrils, twining or clinging. The kind of support may be determined by the type of vine selected.

Tendrils are slim, flexible, leafless stems that wrap themselves around anything they contact. The grape is probably the best known vine that climbs by means of tendrils. Twining vines wind their stems around any available support (figure 3). Clinging vines climb by means of either tendrils with disklike adhesive tips that attach themselves to any surface, or by means of small aerial rootlets along the stems that attach themselves into crevices of a rough-textured surface.

Twining and tendril-type vines climb best on wires, trellises and arbors. They can be grown on flat surfaces only if proper supports are also provided. Clinging vines can be used on either brick or masonry walls. They should never be used on the walls of frame buildings. Their method of climbing has a tendency to damage wood. These vines cling so closely to the wall that moisture is likely to collect under them and cause the wood to rot. Grow clinging vines on trellises far enough from the siding of wood structures to allow for free air circulation behind the vines. The trellis should be removable to permit painting the siding without damaging the vine.

Vine supports should be constructed with sturdy, durable materials. Wire, tubing or wood may be used to make suitable support. Copper or aluminum wire or tubing supports are preferred over other metals, because they will not rust. Redwood, cedar or cypress are the more durable woods for such structures. Structures made from CCA-treated lumber will also have a greatly increased life span.

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Family: Fabaceae (Leguminosae)
The Fabaceae, or legumes, are mostly herbs but include also shrubs and trees found in both temperate and tropical areas. They comprise one of the largest families of flowering plants, numbering some 400 genera and 10,000 species. Peanuts, beans, peas, wisteria and locust trees are among the family.
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