In the spring, wisteria blooms ferociously, producing clusters of lilac-colored flowers on fresh growth that develops from spurs off the main stalks. Check out our Wisteria Growing Guide for more information on wisteria maintenance, including planting and pruning.
About Wisteria
Wisteria is a long-living vining shrub with cascades of blue to purple blossoms that, in the spring and early summer, look stunning hanging from a pergola or archway. However, this vine is known to grow fairly heavy and to grow quickly and aggressively, frequently reaching lengths of more than 30 feet. It’s advised not to put wisteria vines too close to your home since they will squirm their way into any crack or crevice they can find.
Beautifully fragrant wisteria flowers offer a feast for the senses. A brown, bean-like pod remains on the plant during the winter after flowering. There are only blooms on fresh growth.
Note: Be careful when planting wisteria! The wisteria plant contains lectin and wisterin, which are poisonous to people, animals, and even pets. If taken in significant quantities, these poisons can result in anything from nausea and diarrhea to death.
Is Wisteria an Invasive Plant?
The wisteria species Wisteria sinensis and Wisteria floribunda, which are not native to North America, are regarded as invasive in several areas. If you want to add a new wisteria to your garden, we advise choosing one of the native North American varieties, such as American wisteria (Wisteria frutescens) or Kentucky wisteria (Wisteria macrostachya), which are excellent alternatives to the Asian species.
Do you want to know how to distinguish between North American and Asian species?
While North American wisteria is not quite as aggressive in its growing tendencies and has smooth seed pods and fruits in addition to more-or-less cylindrical, bean-shaped seeds, Asian wisteria is an aggressive grower with fuzzy seed pods. Another distinction is that the flowers of American and Kentucky wisterias appear in the late spring after the plant has begun to leaf out, whereas those of Chinese wisteria do not.
When to Plant Wisteria
- Plant during the plant’s dormant season in the spring or fall.
- Wisteria can be grown from seed, although plants from seeds frequently take many years to mature and begin to bloom. It is advised to buy wisteria plants that are already established or to begin with a cutting.
Where to Plant Wisteria
- Put a plant in full sun. Even while wisteria will grow in some shade, it won’t likely bloom. Sunlight is necessary.
- Wisteria should be grown in fertile, wet, but well-draining soil.
- Wisteria will grow in most soils unless it is in bad condition, in which case you need add compost. Find out more about soil improvements and getting the soil ready for planting.
- Because wisteria grows swiftly and can easily engulf its neighbors, pick a location apart from other plants.
- Additionally, wisteria is renowned for encroaching on and infiltrating surrounding buildings like homes, garages, sheds, and so on. We highly advise against growing wisteria too near your house!
- Wisteria vines need a very strong support, like a metal or wooden trellis or pergola, to climb on. Plan carefully and use substantial materials to construct your structure because mature plants have been known to become so heavy that they destroy their supports.
Wisteria looks gorgeous growing up the side of a house, but use caution when planting it because it is a very strong vine that will get into any crack or gap!
Caring for Wisteria
- Apply a 2-inch layer of mulch and a layer of compost under the plant each spring to keep moisture in and keep weeds at bay.
- Phosphorus is often used by gardeners to promote flowering. In the spring, work a few cups of bone meal into the soil. Then, in the fall, add some rock phosphate. Study up on soil amendments.
- If you get less than an inch of rain each week, water your plants. (To determine how much rain you are receiving, set an empty food can outside and use a measuring stick to gauge the depth of the water.)
- During the summer, try pruning the out-of-control shoots every two weeks for more blooms.
Pruning Wisteria
- In the late winter, prune wisteria. Remove at least half of the growth from the previous year, leaving only a few buds on each stem.
- Also prune in the summer after customary flowering if you prefer a more formal appearance. On fresh growth, spurs from the main shoots of the wisteria develop its blossoms. Trim back every new shoot from this year to a spur, leaving no more than 6 inches of growth. So that there are no free, trailing shoots, the entire plant can be trained, roped in, and otherwise organized throughout this procedure.
- Mature plants that have been cultivated informally require little to no more pruning. However, for a plant that has been formally trained, side branches should be pruned back in the summer to 6 inches, then again in the winter to 3 buds.
- Possess you a fresh wisteria? After planting, aggressively prune the vine. Then, the next year, trim the main stem or stems to a height of 3 feet from the growth of the previous year. After the framework has grown to its full size, midsummer extension growth should be cut back to where it started that season.
Types of wisteria:
There are two varieties of wisteria: Asian and American. Although aggressive growers, Asian wisterias are well-known for their stunning blossoms. American wisterias are less aggressive and still produce beautiful blossoms. Compare the most popular wisteria varieties.
Flower color:
Wisteria comes in a range of colors, such as white, pink, and blue tones, in addition to the well-known purple blossoms. If you believe you have seen a yellow wisteria flower, it was probably a golden chain tree (Laburnum).
Foliage:
Wisterias are deciduous, which means that when the weather becomes chilly in the fall, they lose their leaves. The misunderstanding is occasionally brought on by a different vine known as evergreen wisteria (Millettia reticulata).
Avoid planting aggressive wisterias close to your home as they can cause damage and have even been known to destroy buildings.
Wisterias can be grown in full sun or partial shade, but to promote healthy bloom development, make sure the vines get at least six hours of direct sunlight everyday. If you reside in a colder area, pick a planting location that is protected because a heavy spring frost can harm the flower buds.
Create a planting hole that is the same depth as the plant and twice as wide, then level the plant with the soil surface. Because the vines will soon fill in, you should space your plants at least 10 to 15 feet apart along the support structure.
Wisterias don’t need much care once they are planted to promote healthy growth. Water frequently over the first year until the roots take hold.
After planting, wisterias could take some time to come out of dormancy and might not start to leaf until early summer. They will leaf out at the regular time the following spring, but don’t be surprised if they don’t bloom. Wisterias take three to five years to reach full maturity and may not start blooming until then.
Wisterias grow quickly and can reach heights of up to 10 feet in in one growing season. That works out well if you need to quickly cover a fence or pergola but don’t want the vines to take over your landscape. Regular pruning (once in the summer and once in the winter) not only controls wisteria’s growth but also encourages more robust flowering by creating a framework of horizontal branches and causing spurs to grow at regular intervals.
Cut back the current year’s growth to five or six leaves in July or August, or roughly two months after the plant flowers, to get rid of stray shoots and make short branches that will produce flowers the following year. Summer pruning needs to be done more frequently. Re-prune the plant in January or February while it is dormant by removing two or three buds from the growth from the previous year.
The first few years of wisteria’s growth are crucial for creating the desired framework for the plant’s development. As soon as your wisteria begins to grow, start connecting particular lateral shoots to its support structure. You should also cut down any extra growth. An aggressive pruning may be required on elder plants to promote the growth of new branches. Cut down aging branches to the main primary stem to accomplish this. The spaces will soon be filled with new side branches that can be connected back into the support structure.
Visit the Royal Horticultural Society to view a video on how to prune wisteria vines properly.
What is the duration of an American wisteria’s bloom?
Wisteria may get fairly heavy and needs solid supports, therefore when it is planted, care should be made to ensure a suitable structure is being used, such as a sturdy arbor, pergola, or fence.
The young vine needs to be wound or tied to the vertical structure in order to provide Wisteria with some guidance. You can do this by carefully looping the young shoot around the arbor, pergola, or fence’s wooden pillar. Due to the fact that this trunk will enlarge with time, you don’t want to clamp it particularly tightly to the wood. As an alternative, you can teach the branches to grow vertically by attaching a string from the plant’s base to the top of your building. Wisteria is content to scramble across a horizontal surface, so after the vine has established itself on the top half of your building, you can remove it.
Many pieces of gardening literature make the assertion that American hybrid plants are less hardy or less likely to bloom repeatedly. Less tenacious is a pretty relative term, though. We are still dealing with wisteria, which may grow five to ten feet in a single season in robust specimens. Regarding flowering, you will often get a large rush of spring blooms and frequently another flush later in the summer under perfect growing conditions and with the right species for your climate (usually at about thirty percent of the volume of the spring bloom).
Here in the Pacific Northwest, a well-established wisteria should be in its bloom cycle in April or May, with Chinese cultivars blooming before leaf-out and American and Japanese cultivars blooming after leaf-out and just before Chinese cultivars. Sometimes during the growing seasons, very well-kept wisterias will blossom, although never to the extent seen in spring.
Some of you might be shaking your heads and saying, “My plant has never even blossomed once!” This is undoubtedly conceivable and might be connected to one of the following problems:
High-nitrogen fertilizers: If your plant is near a fertilized lawn or if you use one, you will be encouraging a lot of vegetative development at the expense of flowering (nitrogen, phosphorous, and potassium (N-P-K) strength is given numerically on packages, with nitrogen being the first number). Since wisteria belongs to the family of legumes and peas, it may have some nitrogen-fixing abilities, which would increase the fertilizer factor.
Light: Wisteria can thrive in areas with partial shade, but it needs at least six hours of direct sunlight for flowering.
Frost: Just like many spring-flowering plants, flowers or their buds can be harmed or even killed by a cold snap.
Disease and pests: This is quite unusual. Wisteria scale is the largest pest, but it’s not a huge issue in the Pacific Northwest. Wisteria scale has only ever been reported to Swansons once, in my experience. Given the size of wisteria plants and the density of the foliage, systemic insecticides are preferable to foliar treatments for treatment. If wisteria is planted very incorrectly or is cultivated in an area that is overly damp with inadequate drainage, it may occasionally have root rot or graft failure.
Water: Wisteria prefers soils that are fertile, moist, and well-drained. As a result, irrigation to a certain extent can be beneficial, especially if the plant is in a location that is particularly dry given our drier Mediterranean summers.
Wisterias are known for tolerating all types of aggressive pruning, however pruning that is done improperly or at the wrong time will significantly reduce flowering.
Maturity: When a plant is ready to flower, it is referred to as being “adult.” For certain plants, this process can take just one season or years. From seed, wisteria might take 20 years to bloom. Fortunately, this doesn’t happen very often in the nursery industry. The plants we observe, especially the hybrids and cultivars, are grafted or cultivated from rooted cuttings and begin to bloom at a young age—roughly 7 years.
Don’t worry too much if you planted wisteria this year (or perhaps a few years ago) and it didn’t bloom. It may take some time for wisteria to establish itself and begin producing its stunning flower show on a regular basis. Up to 7 years may pass before very young plants begin to blossom freely. However, I have read reports of plants blooming in their first year after planting. Fortunately, producers usually make the plants available to us when they are 4–8 years old, so once planted properly, you won’t have to wait very long for blossoms.
However, there are a few things you may do to encourage flowering the following year if you have an older plant that either won’t flower or does so intermittently (i.e., once every few years).
I’ll start with the fundamentals: root pruning and nutrients. The second article in this series will discuss pruning, which is by far the best strategy for encouraging re-blooming.
Do American wisterias require direct sunlight?
Give your American wisteria a location with wet, well-drained soil and direct sunlight (where the plant will get at least six hours of direct sunlight every day). Although they can tolerate some shade, planting in full sun is the best option if you want to see hundreds of blossoms every spring.
Planting can be done in the spring or the fall. You must create a hole that is two to three times as big and as deep as the root ball in the nursery container. Space your plants at least 10 to 15 feet apart if you’re trying to grow your own version of a wisteria tunnel so that each one has plenty of area for its roots to spread. After you’ve filled the hole, be sure to water thoroughly to help the dirt settle around the plants and cover them with mulch to keep moisture in and discourage weed growth.
Once established in your garden, wisterias are drought-tolerant, but if you don’t get at least an inch of rain, you might still need to water them once a week. Additionally, remember to prune your plant each year in late winter for the finest blossoms. Wisterias bloom on fresh growth, and trimming helps the plant produce additional stems. If you want to maintain a specific shape or height for the plant, you may also cut it back in late summer after it blooms.
The proper wisteria vines can bring beauty to your yard, but the incorrect ones will rapidly turn into troublesome weeds. When purchasing a wisteria, pay special attention to the plant tags and look for variants of the native species; they’ll add beautiful flowers to your yard without being an annoyance.