Here at Gardening Know How we know the importance of arming yourself with easy answers to questions about your precious plants. To help keep your garden looking its best, it helps to have the information you need readily on hand should problems arise. Wisteria plants are beautiful vines commonly planted in home landscapes. While they’re usually trouble free for the most part, they do have their problems. Here are 10 questions about wisteria vines that often come up.
1) Why is my wisteria is not blooming?
There are various reasons why a wisteria isn’t blooming, but the most common is excess nitrogen caused by over-feeding. Excessive fertilizer is likely to blame if the wisteria’s foliage is lush and green, but no blooms are present. If you determine the plant has been over fertilized, you can neutralize the nitrogen in the soil by adding a fertilizer high in phosphorus and potash. Timing of fertilization may also be a factor, as wisteria should be fed in autumn. Other possible reasons for a lack of blooms may be inadequate sunlight, lack of proper pruning or poorly drained soil.
The question of how and when to prune wisteria vines is a common one. Prune wisteria twice a year, in late winter when the plant is still dormant and no new leaves have emerged, and again after blooms have faded in summer. Winter pruning involves cutting long shoots down to three to five buds, and also provides an opportunity to remove unsightly growth that will detract from the appearance of the shrub. Summer pruning is the time to remove or cut unruly green shoots back to five or six leaves, thus controlling the size of the plant. Don’t be afraid to prune hard in summer, removing up to 25 percent of growth.
3) How can I get rid of wisteria vines?
Although wisteria is beautiful, the plant can become aggressive if not properly maintained. The first step to getting rid of wisteria is to prune the plant to the ground, and then apply an herbicide (Roundup works well for this) to the fresh cut, using a disposable paintbrush. Reapply if new growth appears, but trim the stump or peel the bark first so the herbicide can penetrate the wood. Use care, as some herbicides will kill any plant they touch. Herbicides can take up to a month to take effect, but when the vine dies, it’s relatively easy to pull the plant or cut the stump level with the soil.
4) Why are there yellow leaves on wisteria?
Wisteria is a hardy, low-maintenance plant and yellow leaves are common when temperatures drop in autumn. Any other time of year, yellow leaves on wisteria generally indicate a problem that needs attention. For example, the soil may be iron deficient, a problem that can be determined by testing the soil. Yellow leaves may also be caused by wet, poorly drained soil; fungal disease; viral disease; or the presence of pests such as aphids or scale, which are easily controlled with insecticidal soap or neem oil. Usually, yellow leaves on wisteria are easily rectified if the problem is addressed as soon as possible.
5) How do you root wisteria plants?
Propagating wisteria vines from cuttings is the easiest way to start a new plant. Take cuttings from tender softwood in late spring or early summer. Remove leaves from the bottom half of the stem, then dip the cut end in rooting hormone and plant the stem in moist potting soil. Cover the pot with plastic, then place the cutting in bright, indirect light. Water as needed to keep the soil moist but not soggy. Alternatively, you propagate wisteria by planting seeds. This method, however, can take several years to produce a mature, flowering wisteria.
6) Is the root system on wisteria invasive?
Wisteria is spectacularly beautiful, but certain types, including Chinese wisteria and Japanese wisteria, are invasive plants that can choke out native vegetation. This occurs because the roots travel swiftly and unwanted plants may appear a considerable distance from the main shrub, twining around trees or anything else that lies in their path. These plants should be avoided if they are considered invasive in your area. Otherwise, regular pruning and proper care will keep rampant growth in check. In severe cases, wisteria vines must be destroyed.
7) How to plant and care for a wisteria vine?
Wisteria is a hardy, low maintenance plant that provides beauty to the landscape, growing over a sturdy arbor or other supportive structure for many years. Although wisteria prefers deep, rich soil, the plant adapts to most soil types. To produce ample blooms, look for a planting site where the wisteria receives plenty of bright sunlight. Once established, wisteria is a vigorous vine that benefits from regular, bi-yearly pruning, but otherwise requires little water and no fertilizer. Wisteria is suitable for growing in USDA plant hardiness zones 5 through 8.
8) How do you transplant a wisteria?
When moving wisteria plants, it’s better to transplant young wisteria, as a mature plant may not survive the relocation. Ideally, the vine should be pruned and the roots trimmed the autumn before transplantation in early spring. Tie up loose branches on moving day, then dig the wisteria, cutting a wide swath around the shrub to minimize root damage. Pry the plant from the ground with a sturdy shovel, then slide a large piece of cardboard or burlap under the root ball. Plant the shrub in a pre-dug hole in soil that has been amended with compost or manure. Keep the soil moist until the vine is established.
9) Can you save a wisteria damaged by frost?
Wisteria is a tough plant capable of tolerating winter climates as far north as USDA zone 5. However, an unexpected frost in late spring may damage tender new growth. If this occurs, it’s safe to prune cold damaged growth back to a healthy bud or shoot once you are certain any potential danger of further frost has passed. After pruning, feed the wisteria a good quality, general purpose fertilizer and continue to provide proper care. Take heart, as you may not notice signs of recovery until midsummer.
10) Wisteria leaves are turning brown and the vine is dying. Why?
Wisteria is relatively trouble free, but the plant can be affected by a variety of problems that may cause the leaves to turn brown. Poorly drained soil is a common culprit, as soggy soil prevents the roots from receiving necessary oxygen. While wisteria doesn’t typically have much trouble with disease, it may be affected by canker diseases that block water and nutrients. Brown leaves may also be attributed to soil deficient in iron or nitrogen, or conversely, a plant that receives excessive nitrogen due to over-fertilization. Soil issues should be rectified only after the problem is verified with a soil testing kit.
Everyone has questions now and then, whether long-time gardeners or those just starting out. So if you have a gardening question, get a gardening answer. We’re always here to help.