CORVALLIS, Ore. — Wisteria delivers a spectacular spring bloom, but it will overwhelm a garden if it isn’t pruned and supported correctly.
“Wisteria are very vigorous vines and can climb easily to 30 to 40 feet. The most common mistake is not pruning at all.”
“Wisteria are very vigorous vines and can climb easily to 30 to 40 feet,” said Neil Bell, horticulturist with the Oregon State University Extension Service. “They can be quite heavy and should be grown on a strong structure.”
“Before planting one, people should realize the effort involved in keeping them in bounds,” he said. “You can tackle most flowering shrubs once a year, but wisteria is so insanely vigorous there’s an advantage to summer pruning as well as in winter. The most common mistake is not pruning at all.”
Most home gardeners grow the Chinese species, Wisteria sinensis, which blooms on bare branches before foliage emerges and whose flowers open all at once. Japanese wisteria, W. floribunda, opens gradually from the top down and after leaves appear. Both can run aggressively and both should be cut back regularly.
Prune twice a year
Winter is the easiest time to see what needs to go.
- Cut excess growth back to the trunk.
- Shorten remaining runners to two or three buds, about 6 inches, cutting just above a bud.
- Repeat in summer: remove excess growth and clip the rest to two or three buds.
This keeps flower-bearing spurs close to the main framework and prevents the vine from climbing into roofs, gutters or nearby trees.
Train it as a small tree
Another way to manage wisteria is to grow it away from buildings.
- Set a sturdy metal post or other strong support.
- Train a single shoot up the support in the first season.
- The next year, cut the main stem just above the top of the support to form the “head.”
- Prune hard every year to keep the top in bounds; even after strong cuts, wisteria will still bloom.
When a wisteria won’t bloom
Sometimes a young vine takes two or three years — or longer — to flower, especially if it wasn’t in bloom when purchased.
- Avoid high-nitrogen fertilizer.
- Lightly root prune by pushing a shovel in a circle 1–2 feet from the trunk to stress the plant.
- Keep it in full sun.
Stressing the vine often encourages flowering.
Growing basics
- Plant in full sun.
- Use well-drained soil kept evenly moist, not wet.
- Fertilize lightly with a low-nitrogen product once a year, every other year or not at all.
- Provide the strongest support you can — this plant gains weight quickly.
Regional considerations for Oregon
Western Oregon/Willamette Valley
- Generally the easiest place to grow wisteria.
- Summers are warm enough for good flowering, and soils drain reasonably well.
- Stay on top of pruning because vines can get very vigorous here.
Oregon Coast
- Cooler, marine conditions can delay or reduce bloom, especially with Wisteria sinensis.
- Choose the warmest, sunniest, most sheltered spot you have, out of strong coastal winds.
- Good drainage is still important in winter-wet soils.
Southern Oregon
- Plenty of summer heat, so flowering is usually good.
- Vines can grow very fast — plan on consistent summer and winter pruning.
- Irrigate during long dry spells, but don’t overwater in heavy soils.
Central and Eastern Oregon
- Colder winters and drier air mean you should plant in a protected microclimate (south- or west-facing wall, inside a courtyard, or where snow and wind don’t hit as hard).
- Mulch roots in winter to buffer cold.
- Regular irrigation is needed in summer because it’s so dry.
- In colder pockets, winter injury can reduce bloom; if that happens, focus on keeping the framework healthy and try again the next year.
Higher elevations anywhere in Oregon
- Late frosts can nip flower buds.
- Site selection (sun + shelter) matters more than the exact species.
Safety note
Keep in mind that wisteria seeds and fuzzy seed pods are toxic.
Previously titled Wisteria care: Take out clippers twice a year and go to town
