Wisteria is a woody, deciduous vine valued for its long (12-18 inches) racemes of fragrant springtime flowers (most often bluish or purplish, but occasionally pink or white). Flowers are succeeded by bean-like pods in fall. Leaf form is pinnate (feather-shaped).
There are three main types (two Asian and one American). They often look so similar that it's difficult to distinguish between them, but one identifying feature is the pods. Those of Asian type are covered in fuzz; those of the American type are smooth.
While the Asian wisterias are similar in appearance to the American, there are important differences to consider before deciding which type to grow.
|Common Names||Wisteria, Chinese wisteria, Japanese wisteria, American wisteria|
|Botanical Names||Wisteria spp.|
|Plant Type||Deciduous, perennial vine|
|Mature Size||10 to 25 feet long, 4 to 8 feet wide|
|Sun Exposure||Full sun, partial shade|
|Soil pH||Slightly acidic to neutral|
|Hardiness Zones||5 to 9 (USDA)|
|Native Area||Northern Hemisphere|
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.
Both Chinese and Japanese wisteria are invasive in North America. This is another reason why some North Americans prefer to grow American wisteria. If you do grow one of the Asian types, you'll have to spend more time on pruning to keep the plant in check.
Wisteria performs best in full sun when grown in the North. In the South, down in zone 8, however, it profits from afternoon shade.
The most important soil requirement for growing wisteria is good drainage.
Wisteria has average water needs.
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.
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.
Types of Wisteria
Wisteria commonly comes in three species:
- Chinese wisteria (Wisteria sinensis), which can live up to 100 years
- Japanese wisteria (Wisteria floribunda), which arrived in the U.S. from Japan in the early 19th century
- American wisteria (Wisteria frutescens), the smallest species, growing only two-thirds as long as the Asian types
You'll have more trouble getting either of the Asian types to bloom in North America, so American wisteria is the best choice for North American gardeners.
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.
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 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.
How to Grow Wisteria From 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.
Wisteria is a hardy plant, as long as you don't live north of zone 5. No special steps are required to winterize it.
Common Problems for Wisteria
Because it's toxic, wisteria is deer-resistant. It also tends not to be bothered by insects. However, there is a common problem wisteria owners may face:
The failure of an Asian wisteria to flower is sometimes due to excess nitrogen. Since wisteria is a nitrogen-fixer, adding more nitrogen to the soil through fertilizing can lead to such excess nitrogen. Nitrogen can cause energy to go into the production of leaves at the expense of flowers.
If excess nitrogen isn't the issue, there are steps to take to solve the problem:
- Prune the vines annually (if you aren't already doing so).
- Root-prune the plant.
- Transplant the vine to a spot where it will receive more sunlight.
What type of wisteria is prettiest?
Some judge the floral racemes of the Japanese type to be the most spectacular of the three. But it requires full sun for optimal flowering.
What plants are in the fabaceae family?
What is a good companion plant for wisteria?
Clematis, another flowering vine, enjoys the same conditions as wisteria, so you can grow the two on the same support. A clematis with pink blooms will stand out nicely against a wisteria with deep blue or purple blooms. Examples of pink clematis vines are C. montana 'Broughton Star' and C. montana var. rubens.
Safe and Poisonous Garden Plants: Toxic Plants (by Scientific Name). University of California.
Wisteria floribunda, W. sinensis. United States Department of Agriculture.