How to Grow and Care for Japanese Wisteria

Japanese Wisteria (Wisteria floribunda) is beautiful climbing vine known to grace arbors and trellises all over the country. Its smells delight and its colors and blooms dazzle the eyes. But without proper care or placement it can become destructive and a real headache for you and your community.

Of the many wisterias used in landscape design today Chinese wisteria (Wisteria sinensis), Japanese wisteria (Wisteria floribunda), and American wisteria (Wisteria frutescens) are the most common. Japanese Wisteria floribunda was brought to the United States in the early 19th century for ornamental use and has since become invasive in many parts of the country. Before thinking of planting Japanese wisteria, check with local ordinances to see its invasive status.

Japanese Wisteria Care

The key to wisteria care is in timely pruning and the ability to go against instincts and not fertilize. Keeping on track with these two routines will allow you to have a beautiful, healthy wisteria for years to come.

Light

It is important to plant Japanese wisteria in full sun or partial shade to ensure it produces its full number of blooms. (Full sun is considered six hours of sunlight a day.) While this sounds easy, the climbing growth habit of the plant makes this more complex with wisteria. Wisteria likes to climb over structures that often create shade. Creating a structure, like an arbor or a pergola, rather than letting wisteria climb on a house that creates shade will negate this issue and create a new focal point in your yard.

Soil

Wisteria will tolerate various soil conditions as long as they are well-draining and consistently moist but not wet. Wisteria will not do well in wet areas.  It prefers an area with loamy soil that is loose and organically rich. When considering pH levels, it is not tolerant of alkaline or very acidic conditions. It prefers a range of 6.0 to 7.0 pH.

Water

Like most trees and shrubs, wisteria only needs regular watering during their first year. They will benefit from regular watering to help establish their roots. After this first season, wisteria should only need supplementary watering during dry periods. When watering plants, remember long deep watering that is infrequent is better than quick, frequent watering.

Temperature and Humidity

Japanese wisteria is native to a range that is located in a temperate location. It will thrive in areas that are similar to its native habitat being cold tolerant, but it's also sensitive to extreme heat. Its USDA zones are 4-9.

Fertilizer

Less is more when it comes to fertilizer and Japanese wisteria. If planning to fertilize,  do so with a low nitrogen fertilizer (N in the NPK ratio). Fertilizing your plant only once a year or every other year, or even not at all, is acceptable.

If your wisteria is not blooming, you may be over-fertilizing. You can shock the plant into bloom by stopping fertilizing and root pruning.  To root prune, use a shovel to cut the roots in a circle about two feet away from the plant's trunk. Doing this will stress the plant and may force it into bloom.

Is the Japanese Wisteria Toxic?

Yes, Japanese wisteria is poisonous to pets and humans. The seed pods and seeds are the most toxic parts, but all of the plant is toxic and should not be ingested. Contact a doctor if someone has ingested Japanese wisteria, and reach out to a veterinarian if a pet has ingested any.

Symptoms of Poisoning

• Collapse
• Confusion
• Dehydration
• Diarrhea
• Dizziness
• Nausea
• Repeated vomiting
• Severe diarrhea
• Speech problems
• Stomach pains

Pruning

Japanese wisteria flowers bloom on new growth, so you will need to prune twice a year to manage both size and to keep branches close to the main structure to allow for enjoyment of the profuse blossoms. Doing this is an easy task and is done by pruning new growth back to six inches in July or after the wisteria has flowered. This is a really great time to do maintenance pruning and remove any growth not needed for the main structure of the plant and prune away suckers. During the winter or second pruning you will want to remove at least half or the prior seasons growth, remembering that wisteria only blooms on new wood.