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GROWING WISTERIA COMPLEXITIES

written by

Marianne C. Ophardt

WSU Extension Faculty

for the Tri-City Herald, Kennewick, WA

Wisteria is a beautiful woody vine that intertwines over and around structures, creating a romantic, picturesque garden tableau. I’ve always been an admirer of this vine, but there are some complexities that gardeners may encounter when growing wisteria.

Difference Between Japanese and Chinese Wisteria

There is more than one species of wisteria. The two most common ones are Chinese wisteria (Wisteria sinensis) and Japanese wisteria (Wisteria floribunda), native respectively to China and Japan. The Chinese wisteria tends to be favored by gardeners because its showy flowers open all at once before the leaves develop. Its fragrant flowers range in color from violet to blue, purple, lilac, rose, pink, or white.

The Japanese wisteria’s fragrant flowers open more gradually starting at the base of the cluster with bloom beginning at the same time the leaves are starting to grow. There are numerous named cultivars with different flower colors from purple to violet, red-violet, rose, pink, ivory, and white.

Both wisteria are hardy for our area, but Japanese wisteria blooms about two weeks earlier and wraps itself around structures in a clockwise direction. The Chinese wisteria climbs in a counterclockwise direction.

Wisteria that Don’t Bloom

Wisteria are hardy, fast growing woody vines. While they prefer a moist, rich, slightly alkaline soil, they will tolerate more challenging conditions. It’s true that wisterias grow like weeds. In fact, they have become invasive in 19 eastern US states, vining upwards, girdling, and killing native forest trees.

Wisteria are easy to grow, but many gardeners complain that their vines aren’t flowering. That can be a problem. Vines will only start to flower when they reach the mature stage. It can take a vine started from seed over ten years to grow out of its juvenile state. That’s a long time to wait for flowers, even for the most patient gardener. For earlier flowering vines, plant vines started from cuttings or grafted onto rootstocks. Lack of flowering can also be attributed to too much fertilizer, heavy or improper pruning, winter injury to flower buds, or too much shade.

Support Structures Begin to Crack

Another complaint about wisteria from gardeners is that it devours the structures to which it has been trained to for support. Considering that wisteria vines can live 50 years or more when given the proper care, it’s not surprising that this long-lived vine often outlasts garden structures. Good planning can help avoid problems that result when the wisteria start to crush and crumble the arbor, pergola, or porch column to which they’ve become entwined.

I would recommend against growing them close to or on part of your house. Wisteria vines are known for getting underneath siding, roofing, and into gutters. It’s safest to grow them on arbors, pergolas, and wire trellises away from the house. The most durable structures of heavy metal pipe set in concrete work best, but gardeners often prefer wooden structures for aesthetic reasons. Use beams of pressure-treated or rot-resistant wood if you want your structure and vine to last. Bases should be set firmly in concrete. Whatever you use for support, remember these vines get big and heavy.

Pretty but Poisonous

It’s important to note that wisteria flowers are followed by brown four to-six inch seed pods in the fall. All parts of the plant are considered poisonous, but especially the seeds. They contain a particular glycoside, wistarine, which causes severe gastroenteritis when ingested. Children and small animals can be poisoned with just one to two seeds.

Wisteria are pretty vines, but get to know its complex nature before you decide to plant it.

Published: 7/10/2010 9:52 AM

GROWING THE BEAUTIFUL WISTERIA VINE

written by

Marianne C. Ophardt

WSU Extension Faculty

for the Tri-City Herald, Kennewick, WA

A while back one of my readers asked me to write a column about growing wisteria. I have procrastinated satisfying that request because I know so little about wisteria and have never grown one myself. However, I decided it was time to do a little research into the topic and share what I learned with you.

As many of you know wisteria is a type of vine that twine around supports. Within the wisteria genus there are about ten species of these woody climbing vines, some native to the eastern part of the United States and others native to Asia. The Japanese wisteria (Wisteria floribunda) and the Chinese wisteria (Wisteria sinensis) are the two species commonly found for sale in garden stores and nurseries.

Wisteria are members of the pea family and the pods that develop after flowering are typical of other woody legumes. Caution, the seeds and other plant parts contain a toxic glycoside that can cause gastrointestinal problems if ingested. So don’t let children (or adults) eat the seeds.

Chinese wisteria is most popular with gardeners. It is indeed from China and was introduced into North American gardens in 1816. Its habit is a twining vine, but some nurserymen train it into the shape of a tree with a twisting trunk and a flattened top. The Japanese wisteria is from Japan (hence the name) and was introduced to the US in 1860.

Both of these vines twine to a height of 25 feet or more and a length of 90 feet or more. Both have drooping flower clusters with pea-like flowers. The important difference between these two vines involves the flowers. Chinese wisteria bloom in the spring over a short period, making a big display with 6 to 12 inch long gently fragrant, lavender flower clusters. The flowers open before the leaves develop.

The Japanese wisteria is more subtle, with longer 12 to 18 inch fragrant pink or lavender flower clusters that open over a period of several weeks. It blooms in the spring about the same time as the leaves are developing. Each species has cultivars available with the traditional lavender color flowers, but there are also cultivars with white, pink, and purple flowers. An interesting difference between the two vines is the way they “twine and vine.” Japanese wisteria supposedly twine clockwise and Chinese wisteria twine counter-clockwise.

Known fast growing, rampant vines, wisteria aren’t really hard to grow and have been deemed “invasive” in areas of the US that have climates similar to their native habitats. Generally, they will do well if provided with a well-drained slightly acidic to neutral soil. Full sun is a prerequisite for good flowering. They have few insect or disease problems and don’t need excessive amounts of water or fertilizer for good growth or flowering.

While easy to grow, gardeners sometimes complain about their wisteria vines’ lack of flowering. If you plant a wisteria seed or a plant that was started from seed, it can be many years before your vine will flower. This can be quite a disappointment since the main reason for planting wisteria are those beautiful drooping flowers. It can take from five years up to fifteen years before a vine changes from a juvenile to mature stage when it flowers. Gardeners can be patient, but why wait if you don’t have to? Vines grown from cuttings or grafted from mature vines will typically flower sooner, two to three years after planting if trained and pruned properly.

The other thing that gardeners should know about wisterias is their strength. The sinewy trunks and branches of these vigorous vines need strong (STRONG) support, as they have been known to crush and destroy inadequate arbors, pergolas, porch columns, and patio supports. Trained around a tree trunk, wisteria vines can eventually “girdle” or choke the tree to death. It’s advisable to use pressure-treated lumber with hefty dimensions, such as sturdy wooden poles at least six inches in diameter.

Once established and trained to a sturdy structure, regular pruning will keep the vine from taking over and will keep it flowering well. For detailed information on training and pruning wisteria vines, refer to the Ohio State University Extension Fact Sheet, “Growing Wisteria.” It’s available for no charge at http://ohioline.osu.edu/hyg-fact/1000/1246.html

Published: 2/10/2007 10:38 AM

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