Taxonomy and origin
Wisteria is a woody twining vine in the legume family, grown for the long clusters of pea flowers it hangs in mid spring. It climbs by wrapping its stems around whatever it can reach, the way morning glories do, and which way it wraps helps tell the species apart.
Four species are grown in American gardens: Chinese, Japanese, American, and Kentucky wisteria. Chinese wisteria arrived in 1816 as an ornamental, and in the Southeast it crosses freely with the Japanese species. The genus honors Caspar Wistar, an anatomy professor who died in 1818. The wisteria tree at garden centers is this same vine trained onto a single upright stem.
Bloom time
Wisteria blooms in mid spring, in April and May over most of the country. Chinese wisteria opens in May on branches still bare as the foliage begins to expand, and can run into June. American wisteria flowers about three weeks later, after its own leaves are out. Kentucky wisteria is last, carrying blue racemes in June.
Chinese wisteria opens the whole raceme at once, so the show is heavy and short. Japanese wisteria opens each cluster from base to tip as the leaves come out, so it holds color longer. The North American species flower against green foliage.
Wisteria types and cultivars to know
Four species and a few cultivars cover almost everything sold here. Raceme length, hardiness, and whether the type is invasive where you garden decide the choice.
Which wisteria is in your yard
Three details settle it: the twining direction, the leaflet count, and whether the flowers came before or after the leaves. Keys do not always agree on twining direction, so count leaflets before you decide.
Why wisteria will not bloom
A wisteria that grows hard and never flowers is too young or seed-grown, too shaded, pruned at the wrong time, overfed, or its buds died in winter. Age comes first, because time is the only cure. Look at the base of the stem: a bulge means a grafted cultivar, no bulge means a seedling. A grafted or cutting-grown vine usually flowers two or three years after planting, and can take fifteen. A seedling can take fifteen to twenty years, and may disappoint even then.
Shade is the next check, and even slight shade cuts the number of flowers. Wisteria is a legume that fixes its own nitrogen and rarely needs more, so a high-nitrogen feed buys leaves at the cost of flowers, and overfeeding is a standard reason a vine will not bloom. Cutting in early and midsummer costs the coming flowers, and so does heavy pruning. Regular timely cuts build the spurs the plant blooms from.
Water is the quiet one. Next spring's flower buds start forming in late summer, and dry soil between July and September makes them abort. The Royal Horticultural Society tells gardeners to water wisteria through dry spells in those months. A spring frost damages or distorts the developing flowers so they drop before opening. Shredded flowers or teeth marks point to pigeons or mice instead. When everything else checks out, root prune in fall.
The bloom checklist, in order
Work down these checks in order and stop at the first one that describes your plant.
Pruning and aftercare
Wisteria is pruned twice a year, after flowering in July or August and again in January or February, and both cuts land on the same shoots. The summer cut shortens the season's whippy growth so the wood ripens and flower buds can form. The winter cut takes those same shoots back again and leaves the buds close to the framework. Two or three buds, about 4 inches, is the tight end; 6 to 12 inches of last year's flowering wood is the loose end. The cuts work because wisteria flowers on wood grown the previous season, thinner and paler than the older wood behind it.
The most common mistake is not pruning at all, and the summer cut earns its place on top of the winter one because the vine is so vigorous. A young plant is the exception: leave it alone until it has covered its wall or structure, and count on the first three to five years going into the permanent framework.
An overgrown vine can be brought back, slowly. Shorten the long branches hard and take sections of older stem back to just above a strong young branch lower down. Trace each twined branch before you cut it, because on a mature plant the stem you are pulling is often the one worth keeping. Train new growths in as replacements, and flowering returns in two or three years.
What to cut, month by month
The two main cuts fall in the same weeks every year. The rest is upkeep.
Support and planting
Wisteria needs a structure built for a heavy load. The vine can destroy all but the strongest wooden or metal structures, through sheer weight and the constriction of its twining stems. Posts of 6 by 6 lumber or larger, or steel beam construction, are what stands up to it. Keep it off the house: it grows into small spaces and pries them apart as it thickens, putting gutters, shutters and awnings at risk. On a wall, train it as an espalier on horizontal wires of 3 mm galvanized steel set a foot apart.
Plant between October and April; a container-grown plant can go in any time, though autumn or winter is easier to look after. Choose the spot as if it were permanent: an established wisteria does not take well to being moved. Lateral stems run along the ground from the base and root as they go, so walk that ground each season while the shoots still snap off by hand. For a lattice panel or a light trellis, plant a lighter twiner such as clematis and save the wisteria for the arbor.
Height and spread
Wisteria grows 10 to 25 feet, and the real limit is the support it is given. On a garden structure, Chinese wisteria takes that full height on 4 to 8 feet of width, and spreads to 30 feet where a wall gives it room. Turned loose on a tall tree, Chinese and Japanese wisteria reach 70 to 80 feet. The vine thickens as it climbs: old trunks reach 10 inches across and take on a fluted, muscle-like form.
Light
Wisteria wants full sun, six or more hours of direct light a day, and full sun gives the best flowering. Slight shade will not kill it, but it cuts the number of flowers, so a south or west facing wall or pergola is the standard position. Japanese wisteria is shade intolerant, and American wisteria cannot grow in full shade. The light problem arrives slowly, as the trees around the vine add canopy every season. Count the hours the spot gets in June, with every tree overhead in full leaf.
Water
Wisteria is moderately drought tolerant once established, and when you water matters more than how much. Keep the soil moist while the plant is in bloom, and again in August and September while the flower buds form. Dry soil between July and September aborts next spring's buds, so watering then protects flowers you will not see for a year. An established Chinese wisteria will grow on wet or dry sites, but standing water in heavy ground brings root rot.
Soil and pH
Wisteria grows best in moderately fertile, well-drained soil, slightly acidic to neutral. It tolerates a wide range, from acid ground below 6.0 up to 8.0, though at the alkaline end it becomes susceptible to iron chlorosis. Drainage counts for more than richness: a general garden fertilizer buys leaf growth at the cost of flowers. On sandy ground low in potassium, sulfate of potash in spring at half an ounce per square yard covers the gap.
USDA hardiness
Wisteria is hardy through zones 5 to 9 as a genus, and the four species differ at both ends of that range. Chinese wisteria stops at zones 5a to 8b. Japanese wisteria runs colder and wider, 4a through 9b, a full zone hardier than Chinese. American wisteria holds zones 5 to 9. Kentucky wisteria is the cold-climate answer: 'Blue Moon' carries zone 3 to 9 and flowers in zones 3 and 4. Zone numbers for the Kentucky types also run 5a to 9b, so buy 'Blue Moon' by name where winters are hard.
Surviving the winter and flowering are separate questions. A vine can come through a hard winter with every stem alive and still show nothing in spring, because frost damages the developing flowers and makes the buds drop. The Kentucky types open in June, well after the frost window has closed.
Invasive or native: which wisteria to plant
Chinese and Japanese wisteria and their hybrids are invasive across much of the eastern United States; the two North American species are not. North Carolina flags Chinese wisteria as invasive and calls Japanese wisteria aggressive and invasive for its rooting surface runners. Maryland tells gardeners not to plant the three Asian species and to replace what they have. Nationally the genus is not regulated at all. A vine on the garden center bench can be legal and still be the wrong plant for your county.
What makes it invasive is mechanical. The vines shade out mature trees and strangle their trunks with heavy constricting stems, displacing native plants and changing how much light reaches the forest floor. In the Southeast escaped vines occasionally bring trees down under their own weight. Lateral stems root as they travel, and almost no wildlife eats the seed, so water carries it instead. Removal is a campaign rather than an afternoon: cut edges sprout, root fragments sprout, and an established plant persists for years.
If the point is the flower, the native species does the same job with less trouble: American wisteria needs less pruning than the Asian pair and does less damage to buildings. Outside the genus, trumpet vine, trumpet honeysuckle, virgin's-bower clematis and crossvine are the named replacements, though most are not fragrant and flower later than early spring. With an Asian vine already in place, keep it off trees, cut every ground-running stem before it roots, and prune twice a year.
Growing wisteria in a pot or as a tree
A wisteria will grow in a container if you give it a big pot and a compact type. Use a pot of at least 18 inches filled with a loam-based potting mix, and 'Amethyst Falls' is the cultivar named for the job. Training it as a standard restricts its vigor and is what makes a container planting possible. A wisteria on a single stem takes a lot of cutting to keep that shape.
Building the tree form takes several seasons. Start with a young single-stemmed plant and a stout support of 4 to 5 feet, then tip the leader the following February to force sideshoots. Shorten those sideshoots to 6 inches or a foot each winter to build up a head, and in August cut back any shoot not needed to extend it. A metal support works as well as a wooden one, with the main stem cut just above the top of the support to form the head. Strong cuts do not cost the display.
Propagation and longevity
Wisteria is propagated by layering, by cuttings or by grafting, and the method decides how long you wait for flowers. Layering in summer is the easiest and most reliable route at home, while the trade grafts. Seed is the slow road, measured in years where shoots and cuttings are much faster. To try it anyway, sow fresh seed three quarters of an inch deep, soaking dry seed for 24 hours first. If the point is flowers, buy a plant grown from cuttings.
Pests and diseases
Wisteria has few serious pests: Japanese beetles, aphids, leaf miners, scale insects and mealybugs turn up on it, and the diseases are dieback, crown gall and leaf spot, none of them significant. Brown limpet-like bumps on the bark are brown scale. Irregular dark brown blotches with a yellow margin are powdery mildew, which on wisteria shows almost none of the white growth that gives the disease away elsewhere. Yellowing with bright green veins is something else, iron chlorosis from high soil pH or root disease, so test the pH before treating.
What kills a plant happens at the roots and at the graft. Sudden wilting and dieback can come from honey fungus, phytophthora root rot, waterlogging, or vine weevil grubs in a container, and American wisteria takes honey fungus as well. When the top dies back and new shoots come up from below ground, the cause is usually graft failure, and those shoots belong to the rootstock. It is commonest on young plants but turns up on vines 20 years old and more.
What actually goes wrong, most common first
The complaints that come up most often, most common first.
It hits vines that flowered for years, then stopped. Check the base of the stem first: a bulge means a grafted plant, no bulge a seedling with years to go. Then work down shade, a mistimed cut, overfeeding and winter bud kill.
Lateral stems root as they run, so the plant is wider underground than it looks. Cut edges and root fragments resprout, so removal means cutting again and again.
Yellowing with bright green veins is iron chlorosis from high pH or root disease, so test the soil before you spray. Pale mottling in early summer is usually powdery mildew.
New shoots from below ground while the top stays bare mean graft failure. Root disease, waterlogging and vine weevil grubs give the same picture, so dig to the roots before you give up.
The answer is local: Chinese wisteria is flagged invasive in North Carolina, while nationally nothing is regulated. The native species is the way around it.
The discovery comes late, after the vine is in the gutter or under the siding. Trunks thicken to 10 inches, and nothing lighter than 6 by 6 posts or steel holds a mature plant.
Toxicity and pet safety
Wisteria is poisonous, and the seeds and pods are the dangerous end, though the leaves and fruit are toxic too. The ASPCA lists wisteria as toxic to dogs, cats and horses, and names lectin and wisterin glycoside as the toxic principles. The signs are vomiting, sometimes with blood, along with diarrhea and depression. Severity is low for the genus and medium for the native species, and the quantity behind that is small: one or two seed pods can bring on nausea, repeated vomiting, abdominal pain and diarrhea.
Flowers develop into densely hairy pods holding one to four seeds. On Japanese wisteria they run 2.5 to 6 inches long, ripening from midsummer into fall and sometimes staying on the vine into winter. That leaves hard, rattling pods within reach of children and dogs months after the flowers are gone. Sweeping up what falls under an arbor is the answer. Edibility is claimed both ways: Chinese wisteria flowers are named as edible and as a poison part at once, and supposedly edible parts of Japanese wisteria still carry risk. Treat the whole plant as a hazard and none of it as food.
Fragrance and colors
Wisteria flowers are fragrant, and the colors run from blue and purple through pink to white. Scent is the reason it goes near a porch at all, the same reason lilacs do. Chinese wisteria is only mildly fragrant, and the Asian group as a whole runs from mild to strong. The white silky wisteria 'Shiro-kapitan' is highly scented; the native 'Amethyst Falls' is lightly fragrant. The native species also adds dark burgundy and flowers touched with yellow or green to the usual purple. Cluster length runs from 6 inches to a foot and a half.
Meaning and symbolism
What wisteria stands for in a garden comes out of how long it lasts: this is a vigorous, cold hardy, long lived vine. The Chinese wisteria planted at Sierra Madre, California in 1892 is the largest blossoming plant in cultivation, with over 450 feet of stem and around 1.5 million flower clusters a year. Purple and lavender lead the color list for the genus, and the meanings attached to that color sit with purple flowers generally.
Wisteria myths worth dropping
Five ideas about wisteria that will not go away.
The myth: Pruning is what puts the flowers at risk.
The reality: Not pruning at all is the most common mistake with this plant, and the summer cut earns its place because the vine is so vigorous.
The myth: Wisteria is banned from sale, so it cannot be planted here.
The reality: Nationally nothing is regulated, and the rules that exist are state rules. Maryland prohibits the three Asian species under state law and still lets retailers sell them as Tier 2 plants behind a warning sign.
The myth: The wisteria tree at the garden center is a different plant.
The reality: It is the same vine trained onto a single upright stem, and holding that shape takes a lot of pruning.
The myth: Native wisteria is dull and has no scent.
The reality: 'Amethyst Falls' carries lightly fragrant lavender-purple clusters 4 to 6 inches long, and reblooms in mid and late summer.
The myth: You cannot kill a wisteria.
The reality: You can, but not in one pass: cut edges and root fragments sprout, and an established plant persists for years.
What to expect, year by year
A wisteria runs on a longer clock than almost anything else sold as a flowering vine.
Years one and two go to roots and framework. A young vine is left unpruned until it has covered its support, and the first three to five years of cutting build the permanent structure.
Years three to five bring the first flowers on a grafted plant, though the wait can run to fifteen. A seedling is on a different clock, fifteen to twenty years.
After that the vine is a structural object as much as a flowering one, and the rapid growth never eases off. Sucker sprouts keep appearing at the base. When the framework gets away, a hard renovation cuts it back to a main branch or even to ground level.
Flower photos
FAQ
What are the downsides of wisteria?
It flowers late in life, needs cutting twice a year, and grows heavy enough to destroy all but the strongest wooden or metal structures.
Is wisteria poisonous to humans?
The leaves, fruit and seeds are toxic, and one or two seed pods bring on nausea, repeated vomiting, abdominal pain and diarrhea.
How many years does it take for a wisteria to flower?
A grafted or cutting-grown plant usually flowers two or three years after planting, though it can take fifteen. A seedling runs fifteen to twenty years.
Where does wisteria grow the best?
In full sun, six or more hours a day, on a support built to carry the weight. The genus is hardy through zones 5 to 9.
Should wisteria be cut back each year?
Twice a year. In July or August the whippy green shoots come back to five or six leaves; in January or February those same shoots go to two or three buds.
What can I feed wisteria to make it flower?
Nothing high in nitrogen: feeding buys leaves at the cost of flowers. Where a soil test shows phosphorus is short, superphosphate in early spring can push bloom.
What month does wisteria bloom?
April and May across most of the country. Chinese wisteria can run into June, and Kentucky wisteria waits for June.
How do you pronounce wisteria?
It is said wis-TEER-ee-ah, with the weight on the middle syllable.
What is the best type of wisteria to plant?
In the eastern states the native species avoids the invasive problem: 'Amethyst Falls' for a pot, 'Blue Moon' where winters are hard. For the longest clusters, the Japanese 'Macrobotrys' carries racemes 2 to 4 feet long.
How do I know which wisteria I have?
Timing first: the North American species flower after the plant has leafed out, the Asian ones before. Then count leaflets, 7 to 13 on Chinese and 13 to 19 on Japanese.
Interesting tips
- Buy a wisteria in flower. A plant blooming on the bench is old enough to bloom, which no label can promise.
- On an overgrown vine, cut in two moves: take the excess growth back to the trunk first, then shorten what is left, and use the same order after flowering.
- For the longest clusters, look past the two common species. Wisteria floribunda f. multijuga carries lilac blue racemes up to 4 feet long in early summer.
Related Guides & Flowers
Clematis
The climber for a porch column, a lattice panel or anything else that cannot carry the weight of a wisteria.
Lilacs
The other spring plant grown for scent, with its own pruning window that decides whether it flowers.
Types of flowers
The full catalog of flowers on the site, grouped by type, season and color.
Meaning of flowers
What individual flowers have come to stand for, and where those meanings started.
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