Wisteria – Queen of the Vines

“Queen of Vines” – one of the most beautiful and useful of garden climbers. A deciduous woody perennial, it climbs by twining stems that, with age, become twisted trunks making fascinating patterns in winter. In spring the plant overflows with huge, dripping flower clusters. The pea-type leaves form exquisite tracery against the sky or reflected in a garden pool.

The wisterias are big, bold, and not for small gardens – or even for small structures in large gardens. One vine can strangle a young tree, but is handsome over a large, dead trunk. In mild climates where growing seasons are long, the stems can literally “raise the roof” if not pruned firmly and frequently. Any support provided needs to be practically indestructible. Young plants can top seven feet their first year. Established vines can reach fifty feet and keep going. Careful, constant training and pruning are vital. Dense, tangled, and closely matted, a wisteria is monstrous; thinned so it creates a decorative design against an attractive background, it is glorious.

Culture

Wisterias won’t flower fully without full sun. The soil should be deep and rich, well prepared to a depth of at least two feet at planting time, with peat or manure mixed in. Add sand if the garden soil is heavy or clay-like. Keep the roots constantly moist in summer, when flower buds are forming.

After transplanting, wisterias nearly always take their time about leafing out during the first summer. There may be no sign of growth until August. You can keep the plant watered thoroughly, and wait; or nick the bark of the main stem with your finger nail to see if the trunk is alive inside.

Set young grafted plants with the graft-swelling several inches under the soil surface; set older plants even deeper. In cold climates, spring planting is recommended so roots will be well established before winter. Spring or fall planting is fine elsewhere.

For the most and largest flowers, fertilize in the fall, after leaves have dropped. Spring and summer feedings encourage production of foliage. Any general-purpose fertilizer is suitable; but avoid high nitrogen content that favors growth of leaves and stems.

There are varieties of wisteria hardy in nearly every part of the country. Except for a protective mulch for young plants the first winter, winter care is no great problem. Sometimes, however, winter cold or late spring frosts will kill the flower buds. You can take the vine down from its support and cover it with hay, straw, or soil for the winter; or plant shrub or tree standards and wrap them in burlap.

Training And Pruning

The purpose of pruning is to develop sturdy stem-trunks and great masses of flowers. The method and extent depend upon the age of the plant. But before you touch a twig with the pruning shears, it is important to know that, except for native American wisteria ( W. frutescens), the vines flower on growth made during the previous season.

Young plants should be set about a foot away from the permanent support on which they will spend their life. As stems lengthen, remove all except three or four of the strongest. Tie and train these carefully from the beginning, so they grow decoratively, and so they can’t twine around and choke each other. Cut away undesirable or surplus growth at any time, to keep the vine from forming a tangled jungle. Don’t expect flowers until the plant has had time, even several years, to make a sturdy framework of mature wood.

Annual pruning is usually done during July and August, when long stems (but not the three or four left to form a framework) are cut back about halfway. This encourages development of flowering shoots. Venerable plants with too much old wood can be relieved of the excess in late winter or early spring. Prune, then, as lightly as possible so you won’t reduce or delay flowering any more than necessary.

Flowering

Wisterias that grow year after year without flowering are the vexation of many gardeners. The cause may be any of many physiological factors, or a combination of several. If your wisteria does not flower:

The cause may be:

Insufficient sunlight. Full sun is necessary to full flowering – Transplanting may be risky, but necessary unless you can train or spread top growth out where the sun can reach it.

Soil too rich in foliage-producing nitrogen – Avoid nitrogen fertilizers entirely. Dig a circular trench several feet out from the base of the vine, and more than two feet deep. Mix superphosphate with the soil (several pounds for each inch of trunk diameter) and replace it.

Your plant is a seedling, may take as long as ten years to flower – Spend the little extra for one-year-old grafted stock – if possible, plants that have already flowered in the field.

The plant is immature. Stems must reach a certain stage before there is energy for making flowers – While you wait, prune carefully to encourage flower-bearing spurs for next year.

Improper planting and neglect – Prepare soil well before planting. Water regularly in summer when buds are forming. Prune to lighten the vine and admit sunlight to leaves and stems.

Root and top growth out of balance with each other – If the top is overdeveloped in relation to root spread, prune branches severely, even to restricting growth to trunk and one single-stemmed main branch. If the roots are “running wild,” cut off the side roots in a circle two feet away from the base, by forcing a sharp spade down deep into the soil.

Flower buds killed by winter cold - Remove the vine from its support, lay it down, and cover it in winter. Uncover and replace on the support when danger of severe frost has passed.

When all other methods fail to produce flowers, “shock pruning” may work, but it is not guaranteed a sure cure. In late spring, cut all branches back to two or three leaf buds. Repeat every other week until growth stops, in fall; cut out all new runners growing up from the base.

A milder version is to cut back new shoots from the main stem, leaving five or six leaves, in mid-July. By mid-August, when these have made secondary growth, cut the original stems again to three leaves.

From one to three years of this drastic treatment may produce flower buds. Once the plant flowers, it will continue and improve as long as cultural conditions are favorable.

Propagation

Wisterias are propagated by division, ground layering, cuttings of ripe wood in August over bottom heat – and best, by grafting good-flowering varieties onto strong, hardy root stock.

Representative Varieties

If possible, buy from a reliable grower who offers one-year-old grafted stock that has bloomed in the field. Plant with care, and don’t expect lavish growth and bloom the first few seasons.

Wisteria sinensis (chinensis) – Chinese wisteria – The more popular, graceful climber with seven to thirteen leaflets per leaf, and one-inch flowers in drooping clusters a foot long in April and May. It needs winter protection in severe areas. It grows vigorously up to fifty feet or more, and should be severely pruned in mild climates. Almost all the lavender-blue flowers open at once, before leaves unfold. The variety alba has fragrant white flowers. ‘Blue Empress’ is a named variety described as extra vigorous and hardy, with fragrant blue flowers.

Wisteria floribunda – Japanese wisteria – Hardier, grows safely in northern Vermont and New Hampshire. It is less rampant and vigorous, stops at thirty feet. The flower clusters are more slender, less dense, and longer – sometimes to four feet. And there is a wider selection of colors, from white through pink, to flesh-colored, lavender, and deep violet. There is one double-flowering variety.

The pea-type leaves have thirteen to nineteen leaflets. Flowers appear in late May, and last longer because the top flowers in the cluster open first, those below in succession. Barring a spell of wet weather that may cause the top flowers to drop prematurely, the complete cluster may be perfect and full when leaves open. A number of varieties are available:

Wisteria alba – Fragrant white; later, but free-flowering.

Wisteria longissima – Extra-long clusters of lavender flowers. The variety alba is white.

Wisteria macrobotrys (multijuga) - Flower clusters may exceed three feet. rosea – Clusters of pink flowers to eighteen inches long. An improved variety, rosea superba, is also listed.

Wisteria violaceo-plena – Double dark violet flowers in clusters to eighteen inches.

Wisteria frutescens (speciosa) – Native American wisteria, grows wild in Southern states. It produces four-inch clusters of lilac flowers on this year’s growth. Available from wild-flower growers.

Wisteria macrostachya – Kentucky wisteria – Native to the swamps of Illinois and Arkansas, hardy farther north. Twelve-inch clusters of light blue-purple flowers.

Wisteria megasperma – evergreen wisteria – Australian species suitable for California and similar climates. Heavier, dark, evergreen leaves; short clusters of closely packed, fragrant, red-violet flowers sometimes hidden under the foliage in May and June. Will take temperatures to 20∞, but not for protracted periods.

Wisteria venusta – silky wisteria – Fuzzy leaves and fragrant white flowers in six-inch clusters. Hardy in all but severe regions. The variety, violacea, has silky, fragrant, purple flowers.

Family: Leguminosae

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