How Does Wisteria Spread

Background In 1916, Chinese wisteria was first made available as an ornamental plant. Despite being weedy and disruptive, it has been widely planted, grown, and is still highly popular in the nursery industry.

Availability and Habitat Chinese wisteria, which is widely distributed in the eastern United States, has been found to be invasive in at least 19 states, ranging from Massachusetts to Texas south to Illinois. Although established vines will survive and propagate in moderate shade, wisteria likes full sun. Vines cling to trees, bushes, and man-made objects. Although it can tolerate a wide range of soil types and moisture levels, it likes deep, loamy soils with good drainage. Common locations for infestations include the edges of forests, the sides of highways, ditches, and right-of-ways.

Ecological Danger The tough, woody vines firmly entwine themselves around the trunks and branches of the host trees and sever the bark, causing death by girdling. On the ground, new vines that grow from seeds or rootstocks produce thickets that smother and shade out native plants and obstruct the growth of natural plant communities. Canopy gaps that result from dying girdled trees allow more light to reach the forest floor. While this might momentarily benefit certain local species, it also encourages wisteria to grow and spread vigorously.

Plant: a clockwise-climbing, deciduous, woody twining vine with strong, smooth, gray-brown stems that are dusted with tiny white hairs. The diameter of older plants can reach 15 inches or more.
The leaves are complex, alternating, and have 9–11–7–13 leaflets that are egg-shaped with wavy borders and sharply tapering points.
Flowers, fruits, and seeds: Prior to the development of leaves, flowering takes place in April. The flowers are lavender to purple, appear in pendulous racemes or clusters 6-8 (up to 12) in long, and mostly open at once. Individual flowers are 0.8-0.9 in. long on 0.6-0.8 in. long stalks (pedicels). The fruits are green to brown velvety seedpods 4-6 in. long, narrowed toward the base with constrictions between the 1-3 flat,
Spreads vegetatively by creating stolons, which are above-ground stems that develop shoots and roots at irregular intervals, as well as via seed, which in riparian environments can be transported by water.
Look-alikes include the Japanese and American wisterias (Wisteria frutescens), which have leaves that are 7 to 12 inches long, 9 to 15 leaflets that are all the same size, plane margins, tips that are acute to slightly tapering, smooth bright green above, and slightly milky undersides. They bloom in May after the leaves have expanded, with flower clusters that are 4-6 inches long and not particularly pendulous, and individual flowers that are about 3/4 inches long and

Control and Prevention Cut vines to free trees from the weight and girdling caused by modest infestations. Use a systemic pesticide containing glyphosate or triclopyr on the lower cut stem sections. From a seed, new plants may sprout. Long-term planning is necessary (see Control Options).

Do the roots of wisteria spread?

In order to support the massive vine, the wisteria’s root system extends out widely and dives deep. Do wisteria roots exhibit aggression? Yes, wisteria’s root system is highly aggressive. Avoid planting wisteria next to walls or walkways because of its extensive and strong root system. These are easily harmed by a wisteria’s root system.

Experts advise inserting a corrugated panel about 6 feet (1.8 m) long and several feet (1 m) broad beside the plant to redirect the roots if you find a wisteria close to a building or pathway.

How can wisteria be stopped from growing?

Pruning wisteria twice a year is the best approach to prevent it from growing out of control. After the flowers have faded in the early to mid-summer and when the shoots from this year’s growth begin to look untidy, the first pruning should be done. The goal is to remove undesired shoots or suckers and to keep new development close to the main vine as follows:

Trim fresh growth shoots to a length of 6 inches.
Suckers at the roots should be removed.
Cut off any sprouts that the vine’s main support structure doesn’t require.

Since flowers only appear on one-year-old growth, this pruning strategy not only keeps the vine in a tight shape but also enables the blooms to be seen the following year.

How much space can wisteria cover?

Wisteria develops into a huge, mature vine that could grow to be at least 100 feet long. The sturdy stems develop into massive, twisted trunks that are strong enough to topple fences and arbors. It should therefore come as no surprise that mature Wisteria likewise possesses massive, aggressive root systems.

Wisteria vines require substantial roots to anchor the plant because they grow to be so big and heavy. As a result, the root systems spread widely beneath the surface. Wisteria roots can extend up to ten feet deep in old vines that have been growing for many years. Wisteria roots normally grow two to three feet deep. If you grow the vine too close to existing buildings or underground plumbing, wisteria roots may become an issue. However, if the roots encounter something beneath the earth, they will typically work their way around it or proceed in a different direction.

The majority of farmers that experience issues with their wisteria discover that the problem is above ground as opposed to below ground. The roots of wisteria are more likely to grow straight down than outwardly very far. Because the plant climbs, the tendrils and foliage receive the majority of the developing energy. Wisteria can, however, produce suckers from the root system, which you should cut off as soon as you see them to keep the vine in its proper place.

Potential Damage from Wisteria Roots

In rare instances, planting wisteria vines in the incorrect position might result in damage from the vine’s roots. Wisteria is a woody vine, so while it doesn’t often cause issues like big tree roots may, it can nonetheless slink into unfavorable spaces.

There is always a chance that the root system of your Wisteria could harm your septic tank, irrigation system piping, or other underground pipelines, drains, or structures. Wisteria roots, however, aren’t as harmful as some other plants whose roots actively grow outward.

Although uncommon, bigger problems like foundation damage or subsidence are possible. Wisteria roots are unlikely to cause significant harm to your foundation or walls unless you reside in a very old house with flimsy structural underpinnings.

The only possible exception is if your soil is clay-based. Several instances of mature Wisteria roots drying up the soil, causing it to crack, or otherwise weakening the clay in small portions underneath the foundation have been reported. This might result in some little localized settling, but it’s always a good idea to consult a professional if you think your foundation may have been harmed.

There are numerous instances of enormous Wisteria vines flourishing along the brick walls of buildings all around the world. In other situations, the building isn’t being lifted off its foundation or being made to crumble by the roots. It’s actually simply another illustration of Wisteria’s reputation for aggression. When it comes to wisteria, you should concentrate more on managing the growth above ground than you should be concerned about the roots buried in the earth.

A wisteria tree: will it grow?

The invasive roots of Chinese and Japanese wisteria trees can suffocate native species in your garden. Additionally, non-native twining wisteria vines can grow up to 10 feet (3 meters) per season. The fast-twisting purple vine can destroy trees and plants by obstructing their access to sunlight.

The hardy root system of non-native Chinese wisteria is another problem. Once developed, the roots might be challenging to completely eradicate. However, wisteria vines can reappear if you don’t completely remove them.

Ornamental trees are frequently less invasive than wisteria trees because regular trimming regulates their development. For instance, there are no sprawling vines that engulf fences, pergolas, or arbors. Instead, you get a tree with a single stem and a spreading canopy of lovely blossoms and rich vegetation.

Why does wisteria cause issues?

With 15-inch trunks, this vine can grow up to 70 feet quickly. Native canopy trees, understory trees, and shrubs may be suffocated or destroyed by this invasive vine’s heavy weight due to its quick growth and intense shade.

This is a particular issue in the warmer Southern states, where this aggressive and quickly proliferating invasive species is destroying native habitats.

As it climbs, the vine tightly wraps around the trees and bushes, eventually girdling and killing them.

Because native ecosystems have been destroyed, the habitat for many insects, birds, butterflies, and other animals has also been destroyed, leaving them without a place to live.

Can wisteria damage a fence?

Although wisterias (Wisteria synensis) are prized for their profusions of delicate blossoms, the weight of their vines need a substantial support system. Wisterias are tough in USDA plant hardiness zones 5 through 8, but they can harm fences, trees, and even structures like gutters.

Is a trellis necessary for wisteria?

Wisterias thrive in full light, fertile soil, and both. Of the 10 species, three are grown the most frequently: Wisteria brachybotrys, Wisteria sinensis, and Wisteria floribunda, which are native to China, Japan, and the eastern United States (silky wisteria). All three species have significant growth rates and can extend out to a maximum of 20 meters (66 feet) against a wall or around 10 meters (33 feet) in trees. Wisteria can also be trained to grow as a free-standing standard in a big container or border.

Wisterias for pergolas and arches

The Japanese wisteria (Wisteria floribunda) is best exhibited hanging down from a garden structure like a pergola or arch since it has the longest flower sprays (or racemes) of all the species. They entwine in a clockwise motion while simultaneously bearing blooms and leaves. Lilac blue blooms and racemes as long as 1.2 meters (4 feet) are produced by Wisteria floribunda f. multijuga AGM in the early summer.

Wisterias for walls

Wisteria sinensis, often known as Chinese wisteria, blooms in the springtime before the leaves do. For example, Wisteria sinensis ‘Amethyst’ AGM has violet blue blooms with a reddish flush produced in dense racemes to 30cm (1ft) long in late spring or early summer. They twine anticlockwise and the racemes are shorter so they are best presented against a wall.

Silky wisteria (Wisteria brachybotrys), which can be grown against walls or on pergolas, with downy leaves and small racemes of 10-15cm (4-6in). White flowers with center yellow markings, a strong perfume, and 10-15 cm tall sprays of wisteria brachybotrys f. albiflora ‘Shiro-kapitan’ AGM bloom in the spring and early summer.

If you want to cultivate a wisteria in a big container

It is best to choose Wisteria fructens ‘Amethyst Falls’ because of its compact habit and rich clusters of lilac-blue blooms.

Always choose a wisteria that has been developed from cuttings or by grafting when purchasing one because seed-raised wisterias flower less consistently and take longer to bloom. The graft union should be seen as a swelling close to the stem’s base. Unlike species, named cultivars are virtually always grafted. Purchase your wisteria in flower or go with a specific cultivar to avoid disappointment.

Wisterias are offered for sale as container-grown plants at garden centers and online, and you can use the RHS Find a Plant tool to locate particular cultivars.

Wisteria should ideally be planted between October and April. Wisterias grown in containers can be planted at any time of the year, but fall and winter are the easiest times to maintain. Give them healthy, well-drained soil to plant in.

Wisterias bloom best in full sun, so pick a wall or pergola that faces south or west. Although blossoming will be diminished, they will still grow in light shade.

Wisterias are robust climbers that can grow to a height and width of more than 10 meters (33 feet). You’ll need to give support in the form of wires, trellises, or outside buildings like pergolas or arches against a wall. Wisteria can also be grown up a support or taught up a tree to create a standard. A wisteria can be grown in a border or container by being trained into a standard, which reduces its vigor.

If you want to grow your wisteria in a container, you’ll need a sizable one that is at least 45 cm (18 in) in diameter and is filled with potting soil with a loam basis, like John Innes No. 3.

Feeding

Use Growmore or Fish, Blood and Bone on your wisteria in the spring at the suggested rate listed on the packet. Additionally, apply sulphate of potash at a rate of 20g per sq m (1/2 oz per sq yard) on sandy soils (which have low potassium levels). Fertilizers for flowering shrubs or roses are another option.

Feed wisteria in containers using Miracle-Gro, Phostrogen, or another comparable flowering plant food. A different option is to add controlled-release fertilizer to the compost.

Although wisteria has a reputation for being challenging to prune, this is untrue. Once you’ve made it a habit to prune your wisteria twice a year, you should be rewarded with a pleasing flower show.

When you prune regularly, you reduce the excessive, whippy growth from July and August to five to six leaves, or roughly 30 cm (1ft). This increases the possibility of blossom buds budding and permits the wood to ripen. Then, in February, trim these shoots even more to two or three buds, or around 10 cm (4 in), to tidy up the plant before the growing season starts and make it possible to observe the new flowers.

When your juvenile wisteria has completely covered a wall or other garden structure, start the routine pruning to promote flowering.

Small gardens benefit greatly from the training of wisteria as a free-standing standard in a border or container.

Wisteria can be trained to ascend into a tiny tree’s canopy, however doing so could eventually harm the tree. Pruning will be challenging if the plant develops into a huge tree, and a dense leaf canopy will affect flowering.

Increase your wisteria stocks by layering in the summer, taking softwood cuttings in the spring to mid-summer, or taking hardwood cuttings in the winter since seed-raised wisteria can take up to 20 years to flower.

Wisteria is typically propagated via grafting in professional nurseries, however layering is the simplest and most dependable technique for home gardeners.

Established wisteria can produce hanging, bean-like seedpods after a lengthy summer. While wisteria plants grown from seeds are typically of inferior quality, you might want to try growing wisteria yourself.

After the leaves have fallen, gather the seedpods and let them ripen in an open tray.
When the seed is ready, twist open the pod and sow it 2 cm (3/4 in) deep in seed compost.
Before planting if the seed is dry, soak it for 24 hours.

See our commonly asked questions page for a summary of wisteria issues.

Poor flowering

Poor flowering is the most frequent issue for backyard gardeners, and it can be brought on by a variety of factors, such as:

Young plants can take up to 20 years to flower, so acquire a plant that is already in bloom or go with a certain cultivar because they are typically grafted to avoid disappointment.
Examine your pruning methods and timing because early and midsummer trimming will prevent the growth of flowers the next year.
Wisteria flowers best in broad light; deep shadow produces few, if any, flowers.
Water your wisteria during periods of drought from July to September because a lack of water during this time will influence the development of flower buds the next year.
Flower buds may drop before opening as a result of spring frosts, which can harm or deform growing flowers.
Applying sulphate of potash in the spring will encourage bloom production for the next year in soils that may lack potassium.
The damage caused by pigeons or mice can be identified by torn petals or distinctive teeth marks.