When planting your wisteria, you should make sure that it gets placed in a spot that receives full sunlight. Wisteria will grow in partial sun, but this can result in less flowering. You will want to plant your trees while they are still dormant, which is in the early spring or fall. Make sure that your trees have plenty of space to grow, as they will grow into open buildings and through cracks, and are known to grow up to 10 feet in a year. The vines of the Wisteria grow upwards, so make sure to provide the vines with metal or wooden trellises. Some Wisteria get so heavy that the supports will break if they are not built strong enough.
Wisteria trees require a slightly acidic – neutral soil pH and grow in Zones 4, 5, 6, 7, 8, and 9. They belong in the legume family, which means that nitrogen levels in the soil will be regulated by the plant. If there is too much nitrogen, you will notice more leaves and less flowers. Wisteria will grow in almost any soil, as long as it is fertile, moist, and well-drained. Feel free to add compost if your soil is in poor condition. Your plant hole should be dug as deep as the root ball itself and 2-3 times as wide, with plants spaced 10-15 feet apart from each other.
Take care while planting as all parts of the Wisteria are toxic to livestock, pets, and humans if consumed in large amounts.
Caring for Wisteria
If you have not received over 1 inch of rain for the week, your Wisteria tree will need to be watered.
In the spring, you can apply a 2-inch layer of mulch so that the soil stays damp and there is more weed control. You can also add a couple cups of bone meal in the soil in the spring, as well as rock phosphate in the fall.
If your Wisteria is showing signs of dieback, this can be remedied by simply cutting the dead parts off.
Japanese Beetles are a fairly common issue with plants and there are a variety of topical solutions available at the store (i.e. Sevin dust and Diatomaceous Earth can be sprinkled weekly).
Aphids are tiny, green bugs that eat away at the leaves and can be removed by using a spray bottle filled with Dawn dish detergent diluted with water. Make sure to spray the underside of leaves as well as the top, as aphids are small and hard to see.
Leaf miners are small yellow and black flies that do not grow any longer than a few millimeters. They lay larvae that tend to mine down into the leaves, causing damage to them. A close examination of the leaf will show you small, empty tunnels left behind by the leaf miners, with dark larvae visible at the end of said tunnels. Once you notice these tunnels and larvae, you must act fast. One solution is Neem oil, which slows the leaf miner down and keeps them from continuing to tunnel, mating, and flying around. This will not remove them completely and immediately, but continued use will cause them to die out. Make sure to spray both top and bottoms of leaves. White oil will do the same as the Neem oil, and is made by using 1 teaspoon of vegetable oil, 1 teaspoon of dish soap, and just under 500mL of water. Mix well and spray a light, even coat on tops and bottoms of leaves.
Scale insects are small, single-scale-like bugs with waxy coatings. They feed on plants’ sap and can leave behind honeydew residue that can grow sooty mold (black fungus that prevents healthy photosynthesis). Washing only the leaves (do not get into soil) with soapy water. This will wash off the honeydew residue and scale insects.
Mealybugs are small, light-colored, cottony-looking insects that do not have wings. They also feed on the sap of plants. Like scale insects, they leave behind honeydew residue. Neem oil and the Safer brand Insecticidal Soap work to remove these bugs. Spray every 7-10 days and repeat as needed.
Regular pruning should take place in the late winter. Roots should be cut vertically with a sharp shovel, then fertilized with superphosphate. You should remove approximately half of the last year’s growth, with only a few buds remaining per stem.
For formal pruning, you should prune in the summer after the vines are finished flowering. The Wisteria tree produces its flowers on new growth from spurs off the main shoots, which means you should prune this year’s new shoots back to a spur (leaving 6 inches of growth). While in the pruning process, you can also tidy up, train, and tie the plant so there are no loose shoots trailing about. You should cut the side shoots back to 6 inches in summer, shortening them to 3 inches once winter hits.
If you’re having trouble getting your Wisteria tree and vines to bloom, you may want to take a shovel and cut about a foot and a half away from the plant and 8-10 inches down into the soil. Once you damage about half of the roots, the plant should be shocked back into reproducing flowers. It is relatively difficult to hurt Wisteria as they are unrestrained, rampantly-growing, invasive plants. If you had an especially frigid winter the year before, that can affect the rate at which Wisteria will bloom.