Wisteria blooms vigorously in spring, producing clusters of lilac-hued flowers on new growth. In late July, or after flowers have faded, it’s time to prune. Learn more about growing and caring for wisteria vines.
Wisteria is a high-climbing, long-lived vining plant with cascades of blue-to-purple flowers that look spectacular hanging from a pergola or archway in spring and early summer. However, this vine is a fast and aggressive grower—often reaching 30+ feet long—and is known to grow quite heavy. Wisteria vines will work their way into any crook or cranny they can reach, so it’s advised not to plant them too near your home.
Wisteria flowers are beautifully fragrant, providing a feast for the senses. After flowering, a bean-like brown pod stays on the plant until winter. Blooms only appear on new growth.
Note: Plant wisteria with caution! All parts of the wisteria plant contain substances called lectin and wisterin, which are toxic to pets, livestock, and humans. These toxins can cause anything from nausea and diarrhea to death if consumed in large amounts.
Is Wisteria an Invasive Plant?
Chinese wisteria (Wisteria sinensis) and Japanese wisteria (W. floribunda) are not native to North America and are considered invasive species in some states. The native wisteria species, American wisteria (W. frutescens) and Kentucky wisteria (W. macrostachya), are great alternatives to the Asian species, so if you’re planning on adding a new wisteria to your garden, we suggest that you go with one of the North American species.
Wondering how to tell the difference between the Asian and North American species?
Asian wisteria plants are aggressive growers with fuzzy seed pods, while North American wisteria plants are not quite as aggressive in their growing habits and have smooth seed pods and fruits, as well as more-or-less cylindrical, bean-shaped seeds. Another difference is that American and Kentucky wisteria’s flowers appear after the plant has leafed out in the late spring, whereas the Chinese wisteria’s blooms appear before its foliage.
Planting
When to Plant Wisteria
- Plant in the spring or fall while the plant is dormant.
- Wisteria can be grown from seed, but those grown from seed often take quite a few years to reach maturity and produce flowers. It’s recommended to purchase established wisteria plants or start from a cutting.
Where to Plant Wisteria
- Plant in full sun. Though wisteria will grow in partial shade, it probably won’t flower. Sunlight is essential.
- Plant wisteria in fertile, moist but well-draining soil.
- Add compost if your soil is in poor condition; otherwise, wisteria will grow in most soils. Learn more about soil amendments and preparing soil for planting.
- Choose a site away from other plants, as wisteria grows quickly and can easily overtake its neighbors.
- Wisteria is also known for growing onto (and into) nearby structures, such as houses, garages, sheds, and so on. We strongly recommend not planting wisteria too close to your home!
- Wisteria vines require a very sturdy structure to climb on, such as a metal or wooden trellis or pergola. Mature plants have been known to get so heavy that they break their supports, so plan with care and build your structure with hefty materials.
How to Plant Wisteria
- Dig a hole as deep as the root ball and two to three times as wide.
- Space plants 10 to 15 feet apart.
Growing
Caring for Wisteria
- Each spring, apply a layer of compost under the plant and a 2-inch layer of mulch to retain moisture and control weeds.
- Some gardeners swear by phosphorus to aid with flowering. Scratch a couple of cups of bone meal into the soil in the spring and then add some rock phosphate in the fall. Similar claims of increased flowering have been made about liquid tomato or rose fertilizer. Read more about soil amendments.
- Water your plants if you receive less than one inch of rain each week. (To know how much rain you are getting, you can place an empty food can outside and measure the depth of water with a measuring stick.)
- For more blooms, try cutting back the rampant shoots every 2 weeks during the summer.
Pruning Wisteria
Pruning is the secret to good flowering, as wisteria only blooms on new wood.
Prune established wisteria in July or after flowers have faded. Cut side shoots to about 6 inches long, while retaining the climbing branches. This will create lots of short spurs all along the main vines. In late winter, prune the same side shoots, leaving two or three buds on each.
Just don’t make the mistake of never pruning. Do the following at any time:
- When pruning an established but untamed plant, be ruthless. Cut the stem several feet below the desired height; there will be an upsurge of new vegetative (not flowering) shoots in the following spring. Give it space to grow and full sun.
- Remove suckers from the base of the plant to control spread.
- Remove seedpods at will or leave a few for winter interest. If you bring any indoors for display/decoration, be aware that the ambient warmth of the home may cause them to explode.
- Do you have a new wisteria? Cut the vine back severely right after planting. Then, the next year, cut the main stem or stems back to 3 feet of the previous season’s growth. Once the framework is full size, shorten further extension growth in midsummer to where growth began for that season.
- Get more tips for pruning wisteria.
When Your Wisteria Won’t Bloom
Wisteria are notorious for taking a long time to bloom. Don’t expect flowers for 2 to 3 years after planting. Some readers have sworn by this method of “shocking” the plant to spur on blooming:
- Take a shovel and drive it 8 to 10 inches into the ground about a foot and a half away from the wisteria’s main trunk to slice into some of the roots.
- Damage about half of the roots and the bush will be shocked into reproduction (flowering).
- Don’t worry—it’s difficult to hurt this rampantly growing, unrestrained, often-invasive plant!
Failure to flower may also be due to frigid winter temperatures that have injured the flower buds, excessive nitrogen fertilizer that has promoted foliage over flowers, and/or insufficient sunlight.
Types
Native Wisteria
If you are located in North America, consider planting a species of wisteria native to the continent, such as:
- American wisteria (W. frutescens) grows in Zones 5 to 9. It’s native to a range of states covering Virginia to Texas, southeast to Florida and north up through New York, Iowa, and Michigan. The vine grows 25 to 30 feet long with shiny dark-green leaves and large, drooping lilac or purple-blue flower clusters, which appear after the plant has leafed out. The blooms will only appear on new wood. However, note that the flowers tend to be more lightly fragrant than the Asian wisterias’ flowers.
- Kentucky wisteria (W. macrostachya) grows in Zones 4 to 9. This late-season bloomer is native to the southeastern U.S. and is similar to American wisteria (it is sometimes considered a variety or subspecies of American wisteria). Kentucky wisteria bears mildly fragrant bluish-purple flowers after growing only 2 to 3 years, making it the quickest wisteria to bloom.
- ‘Blue Moon’ is an extra-hardy cultivar of native Kentucky wisteria, with showy silvery-blue clusters. It blooms in late spring or early summer. It’s cold hardy to –30°F.
Non-Native Wisteria
- Chinese wisteria (W. sinensis) and Japanese wisteria (W. floribunda) are non-native, invasive species, so we do not recommend them for North American gardens, despite the fact that they are regularly sold at nurseries and garden centers. They are hardy in Zones 5 to 9 and are capable of growing 30 to 60 feet in length (and beyond in the Southern U.S.). Two common varieties of Japanese wisteria include:
- ‘Honbeni’ (syn. ‘Honko’): popular, bears clusters of pink flowers in late spring
- ‘Alba’ (syn. ‘Shiro Noda’): bears lovely clusters of pure-white flowers in late spring
Wisteria roots are known to have damaged septic systems and lateral lines. Plant the wisteria as far away as you can from your septic system. The roots are extremely strong and vigorous.
Hi Gloria,
It's important to prune old wisterias. Prune the out of control vine as close to the main stem as possible. You can also dig down and cut part of the root that the vine is attached to. Your wisteria is well established and moderate to heavy pruning will not hurt it.
Wisteria have been known to "sleep" for years (est 12 to 15), so it may be entering such a period. You can't know now. Pruning, even a little each year—in spring—can help to promote flowering, but too much pruning can have the same effect (although that's not your problem).
Did you fertilize it? Excess nitrogen fertilizer can cause few/no blooms. Another source suggests that it may be going through a growth spurt instead of flowering.
An extreme cold may have killed the buds.
You can try to "wake it up" with a shovel. However, because flower buds form in late summer, understand that it will not flower this year.
Good luck—
A "good pruning" is impossible for us to define. Pruning wisteria can promote flowering. However, the time to prune is after it flowers. The plant sets buds in late summer to fall.
If it was severely pruned, it may need time to adjust and start growing again.
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