When it blooms in May, wisteria is a show-stopper for a few weeks. The bushy, long-lived wisteria, however, has many advantages. Summertime velvety pod development is followed by good fall color.
But there is a price for all that beauty in the winding and twisting. When left unchecked, wisteria has an aggressive character comparable to ivy and can engulf a home or landscape. However, if you require protection immediately or have hard clay soil where few plants can take root, grab a wisteria.
Is clay soil excellent for wisteria?
Wisteria isn’t particular, so is clay soil off limits? In terms of soil type, wisteria is adaptable. It thrives in slightly clayey soil and may even grow in very heavy clay, but you may need to take precautions against iron chlorosis and root rot.
If your Wisteria is growing in clay soil, it’s crucial to avoid overwatering because Wisteria needs soil that drains easily, which clay does not. Wisteria can drown or develop root rot in wet soil. For information on how to encourage Wisteria to flourish in clay soil, see the section below on soil amendment.
In heavy clay soil, wisteria may also have more trouble absorbing iron. Applying some chelated iron can assist if you detect yellowing leaves with green veins—the typical sign of iron chlorosis.
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You can keep your wisteria vines looking excellent by following these growing guidelines.
Where space permits and gardeners are dedicated to keeping them in check, wisteria are tenacious, twining vines that are used widely in landscapes. They possess endurance, vitality, longevity, and the capacity to scale great heights. They are highly prized for their springtime huge, pendulous flower clusters. Pea-like flowers come in a variety of colors, including white, pink, lilac blue, bluish purple, and purple. The fruit, a long, flattened, green pod, is not particularly attractive. The plant has alternate, pinnately complex leaves and climbs on twining stems. An inch-plus-diameter twisted, woody trunk is not uncommon in older, more established plants.
Wisteria needs full sun (six or more hours of direct sunlight per day) and a deep, somewhat fertile, moist soil that does not dry out too much in order to blossom successfully. Although they can adapt to most soil types, they perform best in neutral to slightly acidic soils with a pH of 6.0 to 7.0. Since mature plants can be fairly heavy, some sort of support will be required.
Plant establishment will be ensured by thorough site preparation. To find out whether the soil’s pH or phosphorus level has to be corrected, perform a soil test first. If so, as you are preparing the soil, add more components. In an area that is two to three feet in diameter and 18 to 24 inches deep, prepare the soil. To enhance soil aeration and drainage, mix one-third by volume of peat moss, compost, or well-rotted manure into the native soil.
On wires, trellises, arbors, and pergolas, wisterias grow best. If the right supports are present, such as rows of wire anchored four to six inches from the wall, they can be grown on solid, vertical surfaces. Use strong, long-lasting materials like wood, tubing, or galvanized wire. Since they don’t rust, copper or aluminum wire or tubing is chosen over other metals. For pergolas and arbors, pressure-treated wood should be used. However, avoid planting wisteria where the stems can encroach on building gutters and obstruct them. Wisteria can also be cultivated as a tree-form or a single trunk standard. The plant needs to be staked upright in order to do this. Its top is severed when it reaches a height of four to five feet. On the top of the stem, side branches are allowed to grow, but the lower stem is regularly pruned. Each winter, side branches are clipped to a length of six to eight inches until the top reaches the appropriate size. Future pruning is removing secondary branches that form immediately after the first or second leaf and trimming summer shoots as soon as they reach their sixth or seventh leaf. These secondary shoots are pruned back in the winter to just an inch from their base. The use of living trees as support is common, but it must be done cautiously. By girdling the stem of the twining wisteria, trees with a diameter of less than ten inches can be quickly killed. Damage to larger trees is also possible. To prevent girdling, trees that are used should be monitored periodically. The previous girdling stem must be physically removed from the tree to prevent further damage if a tree is being girdled; however, the wisteria can be cut back to the soil line and allowed to grow again.
The vine can be planted once the soil has been prepared and the support structure is in place. Put the plant’s root ball in the hole so that it doesn’t go any deeper than where it grew in the nursery. Set your grafted wisteria so the graft union is just below the soil’s surface if it is. The prepared soil mixture should be poured into the hole and compacted around the root ball. After planting, thoroughly wet the area. An inch of water per week, provided either through irrigation or rainfall, is needed for new plants. Young plants should receive annual fertilization until they occupy the designated space. Young vines won’t likely bloom because vegetative growth is being promoted. If the branch and foliage development and color are healthy and the plant has filled the designated space, do not fertilize. Only water if the foliage starts to wilt, which could happen during a drought. Both of these methods reduce floral production while promoting vegetative growth.
To maintain plant quality, some annual pruning is necessary; it is not recommended to let the vine grow haphazardly and take over neighboring plants and buildings. Pruning will encourage flowering and help the vine become less vigorous.
Choose a strong, upright stem to act as the primary leader and attach it to the support to train plants on a wire trellis or an arbor. other side sprouts, remove them. As the primary leader expands, it will form side branches that will later generate additional shoots and flower buds. To create a framework that fits the designated space, keep training the main leader upward and the new side branches as necessary (allow about 18 inches between side branches). When the main leader reaches the desired height, pinch it off.
Where do I put wisteria plants?
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.
Other problems
A mature, seemingly robust wisteria will occasionally pass away and be replaced by a new, healthy branch emerging from the ground. Failure of the wisteria graft may be the reason of this.
Wisteria is sensitive to both of the fungi that cause phytophthora root rot and honey fungus, which are less frequent causes of failure.
Unusual brown blotches and marks on the leaves, typically with a yellow edge, may be a sign that a fungus has infected them. Viruses can also harm wisteria and powdery mildew.
Infestations of scale and, less frequently, wisteria scale can affect wisterias.
While we hope this information may be useful to you, we always advise reading the labels on your plants that provide care instructions.
How much sun is required for wisteria?
The greatest way to utilize wisteria’s breathtaking beauty and incredible vitality is to grow it as a little tree, or standard. Long racemes of sweet-smelling May flowers hang down from soft, pruned leaf heads and sway slightly with each breeze. The compact head of a Tree Wisteria looks amazing in a mixed bed of perennials, bulbs, and annuals. The impression is beautiful and dignified.
Please be aware that wisterias typically take a while to emerge from dormancy after planting. Please be aware that your plant won’t start to leaf out until early summer. It will thereafter leaf out at the usual time in succeeding years (midspring).
Choosing a Location: Wisterias grow and flower most effectively in areas with plenty of sunlight, preferably at least 6 hours every day. They do well in any kind of soil as long as it drains well.
In order to plant your bareroot Wisteria, take off the packing and give the roots a few hours in a bucket of water. Then, dig a hole that is both large enough to permit the roots’ spread and deep enough to allow you to set the crown, or the location where the stem and roots converge, 1 inch below the soil’s surface. Insert the roots into the planting hole and arrange them naturally or like the spokes of a wheel. The roots of many woody plants are brittle, so use additional care when positioning them in the planting hole to prevent breaking them. With one hand holding the crown 1 inch below the soil’s surface, use the other to push soil into the hole while circling the roots to prevent air pockets from forming. Then, using both hands, compact the soil close to the crown. To create a basin, create a rim of earth around the perimeter of the planting hole. This basin is used to collect, hold, and direct water to the roots. Finally, thoroughly immerse the plant.
Please be aware that once bareroot plants are taken out of their packing, they dry up rapidly, especially on a sunny, windy day. Until you are ready to plant, we strongly advise that you keep the roots wrapped in wrapping material.
Staking: To keep their heads aloft in severe gusts, tree wisterias need additional support. After planting, drive the wooden stake that came with your tree 6 to 12 inches deep and 1/2 inch away from the plant’s trunk into the earth. Using the plastic tie tape that came with the tree, affix the trunk to the stake numerous times, spacing them apart by about 8 inches. You’ll need to swap out the original stake for a bigger wooden stake or a sturdy steel pipe as the head and trunk grow bigger. Check the tree every spring and autumn to ensure that the stake is securely in place and that the tie tape used to attach the trunk to the stake is not excessively tight and preventing the trunk from expanding. Plants need to be firmly staked at all times.
Watering and Fertilizing: To hasten wisterias’ establishment in the first year after planting, they require the equivalent of 1 inch of water each week. If the sky doesn’t provide enough moisture, water deeply once a week. Plants that are established only require irrigation during extended dry spells. Wisterias don’t need much, if any, fertilizing because too much fertilizer prevents blossom. Give plants a gentle feeding of 5-10-10 or 5-10-5 at a rate of 3/4 cup per square yard in the early spring each year if your soil is particularly weak or sandy.
Overwintering: For the first few winters after planting, cover the main stem with a piece of plastic tubing in cold-winter conditions like ours here in Litchfield (Zone 5 [-20F]). To encircle the stem, make a straight incision from one end to the other and pry the cut open. (Precut tubing could be available at your nearby garden center.) To stop wind and frost from damaging branches on older specimens, cat’s-cradle bind the branches together using twine to form a web of intertwined strings.
Pruning: Tree Wisterias need to have the long, twining branches they generate in the summer pruned lightly but frequently in order to maintain the globe shape of the head. A couple of weeks prior to the first date of your first frost, they also require one severe pruning in late summer or early fall. Remove all branches that are in the wrong place and reduce the current season’s development to just 5 to 6 huge buds (leaving stubs that are about 6 inches long). This drastic haircut inhibits growth and promotes the transformation of some leaf buds into flower buds. Don’t let pruning errors keep you up at night. Wisterias are highly understanding plants; strong growth the following season will give you another chance.