Wisteria

Wisteria plants are deciduous and famed for their fragrant flowers. Their purple flowers twine up trellises, making them perfect for your garden.

I. Appearance and Characteristics 

Wisteria is a genus of flowering plants in the legume family, Fabaceae (Leguminosae). The genus includes four species of woody twining vines that are native to China, Japan, Korea, Vietnam, southern Canada, the Eastern United States, and north of Iran. They were later introduced to France, Germany and various other countries in Europe. Some species are popular ornamental plants. The genus name is also used as the English name, and may then be spelt ‘wistaria’. In some countries in Western and Central Europe, Wisteria is also known by a variant spelling of the genus in which species were formerly placed, Glycine. Examples include the French glycines, the German Glyzinie, and the Polish glicynia.

Wisterias climb by twining their stems around any available support. W. floribunda (Japanese wisteria) twines clockwise when viewed from above, while W. sinensis (Chinese wisteria) twines counterclockwise. This is an aid in identifying the two most common species of wisteria. They can climb as high as 20 m (66 ft) above the ground and spread out 10 m (33 ft) laterally. The world’s largest known wisteria is the Sierra Madre Wisteria in Sierra Madre, California, measuring more than 1 acre (0.40 ha) in size and weighing 250 tons. Planted in 1894, it is of the ‘Chinese lavender’ variety.

The leaves are alternate, 15 to 35 cm long, pinnate, with 9 to 19 leaflets.

The flowers have drooping racemes that vary in length from species to species. W. frutescens (American wisteria) has the shortest racemes, 5–7 centimeters (2.0 – 2.8 in). W. floribunda (Japanese wisteria) has the longest racemes, 90 centimeters (35 in) in some varieties and 120 centimeters (47 in) or 200 centimeters (79 in) in some cultivars.

The flowers come in a variety of colors, including white, lilac, purple, and pink, and some W. brachybotrys (Silky wisteria) and W. floribunda cultivars have particularly remarkable colors. The flowers are fragrant, and cultivars of W. brachybotrys, W. floribunda, and W. sinensis are noted for their sweet and musky scents. Flowering is in spring (just before or as the leaves open) in some Asian species, and in mid to late summer in the American species.

The seeds are produced in pods similar to those of Laburnum, and, like the seeds of that genus, are poisonous. All parts of the plant contain a saponin called wisterin, which is toxic if ingested, and may cause dizziness, confusion, speech problems, nausea, vomiting, stomach pains, diarrhea and collapse. There is debate over whether the concentration outside of the seeds is sufficient to cause poisoning. Wisteria seeds have caused poisoning in children and pets of many countries, producing mild to severe gastroenteritis and other effects.

II. How to Grow and Care

Wisteria is a large vine best-suited to a spot where it has plenty of room. The trunk becomes massive eventually, attaining a weight that would topple weak supports. Give this twining vine a sturdy arbor for support. Wisteria is a toxic plant, so exercise caution when growing it around kids and pets.

Sunlight

Wisteria performs best in full sun when grown in the North. In the South, down in zone 8, however, it profits from afternoon shade.

Temperature and Humidity

Wisteria on occasion is successfully grown in zone 9, but further south than that, the climate is too hot and humid to grow wisteria.

Watering

Wisteria has average water needs.

Soil

The most important soil requirement for growing wisteria is good drainage.

Fertilizing

Use fertilizer high in phosphorus (the P in the NPK). Because wisterias belong to a plant family known for its nitrogen-fixing ability, don’t fertilize them with nitrogen. They have enough already.  Early spring is the best time to fertilize.

Pruning

As with any plant, prune off dead, damaged, or diseased growth whenever you spot it. 

Asian wisterias need regular pruning to keep their shape. Since they’re vigorous and spread through runners, you must prune yearly to restrict their growth. The less vigorous American wisteria requires less pruning.

Prune wisteria yearly in two stages:

• Prune in late winter. Prune off at least half of the prior year’s growth, but leave a few buds on each stem so as not to spoil the floral display. Don’t prune back a mature vine too far. While it should eventually sprout again, it may take a while for optimal flowering performance to return.
• Prune a second time when blooming is finished (late spring or early summer). This second pruning is to tidy the vine up, for the sake of appearance. Prune off stray shoots to improve the plant’s shape.

Propagation

Cuttings

To propagate, choose a green, non-woody stem in late spring or early summer and cut right below a node (sterilize pruners first with alcohol). A cutting should have two sets of leaves and a node; it should be four inches long. Once you have the cutting:

• Fill a pot with sterile soilless mix.
• Poke a hole in the soilless mix.
• Dip the cutting’s end in the rooting hormone and insert it into the hole.
• Water the soilless mix. To help retain moisture, make a tent over the pot with a plastic bag.

Seed

To grow wisteria from seed, the temperature has to be about 65 degrees Fahrenheir or warmer. To propagate via seed in spring:

• Use soilless mix and a tent as when taking cuttings.
• Soak seed overnight in lukewarm water.
• Sow one inch deep.
• Keep the soilless mix moist. Don’t let the soil dry out completely.

Potting And Repotting 

Wisteria can be grown in a pot, but this is most suitable for vines trained into tree form (also called a standard). The better-behaved native wisterias are a good choice for containers. Wisteria is a heavy plant, and you may only want to pot it once. Choose a sturdy pot that is 18 inches or wider in diameter. Use well-drained soil and stake the plant as discussed above. Water regularly during the first growing season, and provide 1 inch of water a week in subsequent years (more water may be beneficial during hot, dry spells). Fertilize once each spring with a low-nitrogen, bloom-boosting fertilizer.

Overwintering

Wisteria is a hardy plant, as long as you don’t live north of zone 5. No special steps are required to winterize it.

Pests and Diseases

Wisteria plants have few serious problems. Japanese beetles, aphids, leaf miners, scale insects, and mealybugs can be attracted to the plant. If infestation becomes a problem, spraying insects with a strong stream of water, picking them off and putting dropping them in a can of soapy water, or using insecticidal soap may help.

In the case of leaf spots, simply pick off and dispose of affected leaves. Powdery mildew can coat the leaves with a grayish-white mold, but usually doesn’t cause a problem. You can spray leaves with fungicide if the plant’s health is affected.

Wisteria sometimes develops crown gall, a lump of gnarled wood on the stem. Crown gall is essentially a tumor caused by bacteria and cannot be treated. An established plant may survive for years with crown gall, but a newer plant should be pulled up and disposed of in the trash. If you prune a wisteria with crown gall, you’ll need to sterilize your pruners afterward with a 10-percent solution of household bleach.

Honey fungus can attack wisteria from the soil. Symptoms include cracking at the base of the stem, white fungal growth at the base, and gradual dying of upper branches. Sometimes honey-colored mushrooms will appear at the base. Unfortunately, honey fungus can’t be stopped once infection occurs.

III. How to Get to Bloom

A lack of blooms is the most common problem home gardeners have with wisteria. If spring has passed you by without any sign of lovely lavender flowers, consider the following:

New transplants usually take two or three years to settle into your garden before they start blooming.

A late frost may have zapped the flower buds in spring.

Too much nitrogen fertilizer will prevent the plants from blooming. Stick to bloom-boosting fertilizers that are high in phosphorus.

Wisteria do not bloom in full shade and even partial shade, depending on the species. Increase light exposure if needed.

Pruning practices can make a difference. Pruning is best done right after flowering and should be done every year. Japanese wisteria blooms best when new shoots are cut back to three or four buds.

If all else fails and another bloom-free year passes you by, you can try root pruning your plant in fall to encourage it to bloom the following spring. Take a sharp spade or shovel and cut straight down through the roots around your plant. Make a circle about 2 feet from the main stem.

IV. Uses and Benefits 

• Ornamental uses

Wisterias are a group of woody, climbing vines that often boast purple, blue, violet, or white flowers in the springtime, which have spurred their use as ornamentals.

• Art and symbolism

Wisteria and their racemes have been widely used in Japan throughout the centuries and were a popular symbol in mon (family crests) and heraldry. Wisteria is one of the five most commonly used motifs in the mon, and there are more than 150 types of wisteria mon. Because of its longevity and fertility, wisteria was considered an auspicious plant and was favored as a mon, and was adopted and popularized by the Fujiwara clan as their mom.

One popular dance in kabuki known as the Fuji Musume (or ‘The Wisteria Maiden’), is the sole extant dance of a series of five personifying dances in which a maiden becomes the embodiment of the spirit of wisteria. In the West, both in building materials such as tile, as well as stained glass, wisterias have been used both in realism and stylistically in artistic works and industrial design.

V. Harvesting and Storage

Droopy wisteria blooms are spectacular in a bouquet. 

• Gently cut a branch with just-opened flowers. 
• Recut the branch at an angle or cut straight up the bottom of the stem to allow more water intake.
• Remove most of the leaves and place them in a sturdy vase. 
• Vase life is about 7 days.