When does wisteria bloom?

How To Get Wisteria To Bloom – Fix Wisteria Blooming Problems

Wisteria is a vine that is well known for its vigorous growth and are just as notorious for being reluctant to bloom. When a wisteria won’t bloom, many gardeners get frustrated and ask, “Why is my wisteria not blooming and what is the secret on how to get wisteria to bloom?” There is no secret to fixing wisteria blooming problems. A little knowledge can help you quickly fix the problem. Let’s take a look at what you need to do to understand how to get a wisteria to flower.

Reasons Why a Wisteria Won’t Bloom

The most likely reason your wisteria won’t bloom is due to too much nitrogen. When a wisteria plant has too much nitrogen, it will have plenty of foliage growth, but very little and maybe no blooms.

Another reason for wisteria blooming problems is the environment they are growing in. Wisteria vines that lack full sun or proper drainage may be stressed, and while they will grow leaves, they will not bloom.

Improper fertilization may also be the answer to the question of why is my wisteria not blooming. Fertilizing in the spring can encourage leaf growth and discourage blooms.

Lack of maturity may also be the culprit. Most wisteria bought in plant nurseries are the proper age to start blooming; but if your wisteria was grown from seed, or given to you by a friend, it simply may not be old enough to flower yet. Wisteria must be seven to 15 years old before they are old enough to bloom.

The last, and least likely, reason a wisteria won’t bloom is over pruning. Over pruning will remove the flower buds. It is extremely difficult to over prune a wisteria, though.

How to Get Wisteria to Bloom

Since too much nitrogen is the most common cause of wisteria blooming problems, the easiest thing to do is to make sure this is not a problem. There are two ways to correct this cause of a wisteria not blooming. The first is too add phosphorus to the soil. This is done by applying a phosphate fertilizer. Phosphorus encourages wisteria blossoms and helps to balance out the nitrogen.

The other way to reduce the amount of nitrogen a wisteria plant is getting is to root prune the plant. This is done by taking a shovel and driving it into the ground in a circle around the wisteria. Make sure that you do root pruning at least 3 feet from the trunk, as root pruning too close to the plant can kill it. Using root pruning as a way how to get a wisteria to flower reduces the amount of roots and, by default, the amount of nitrogen those roots take up.

If these methods do not work to correct your wisteria blooming problems, you can check to see if one of the other reasons may be the problem. Is the plant getting enough sun? Is there proper drainage? Are you fertilizing at the right time, which is in the fall? Are you pruning properly? And is your wisteria old enough to bloom.

Wondering why is my wisteria not blooming is frustrating when you don’t know the answer. But now that you know how to get wisteria to bloom, you can start to enjoy the lovely flowers a wisteria produces.

You can spot the graft three or four inches above soil level – it will look like a knobbly “thumb” where the flowering variety meets the rootstock. Not only do grafted plants flower more reliably than those propagated by other means, but they also flower in their youth rather than maturity.

A sunny south or west-facing wall is the best position and you need to prepare the ground carefully beforehand by working in lots of well-rotted organic matter. Attach some horizontal wires to the wall at 1ft intervals so that the stems can be unwound from their cane and tied in, and space them out as they grow.

You need not keep them all. Once more stems are produced than you need to cover the area, snip off any that you don’t need. Twice-yearly pruning is best for mature plants – once in July and again in January. An occasional feed with rose fertiliser – in March and June – is all that is necessary to fuel their display. And, hey-presto, the feat is gone and you now know just what to do.

So get out there, choose your spot and then choose your plant for 100 fragrant springs to come.

Don’t miss Alan’s gardening column today and every day in the Daily Express. For more information on his range of gardening products, visit alantitchmarsh.com.

How to grow wisteria

Wisteria makes a fabulous statement on a wall, fence or pergola.
Image:

Wisteria is the quintessential climber for the English cottage garden and an absolute joy in May and June when the beautiful, scented pendants of flowers create a breathtaking display.

But often gardeners find these climbing plants a little daunting – the idea of all that pruning and training feeling far too complicated. It’s a shame because growing wisteria is much easier than you might think. In fact, with the correct care these long-lived climbers will reward you with many years of pleasure.

Choosing a wisteria

Wisteria Sinensis or Chinese Wisteria has shorter blooms than its Japanese cousin.
Image: Christian Mueller

If you’re planning to buy a wisteria, check that the plant is grafted because wisteria grown from seed can take up to 20 years to flower. All of Thompson & Morgan’s wisterias are supplied as grafted plants, so you should only need to wait a couple of years before you’re rewarded with your first fabulous display.

There are lots of cultivars available but most are produced from two species – wisteria sinensis (Chinese wisteria) and wisteria floribunda (Japanese wisteria). Here are the main differences between them:

Species Stems Flowers Approximate flower length
W. sinensis Twine anti-clockwise Appear before the foliage develops 23-30cm (9-12″)
W. floribunda Twine clockwise Appear at same time as foliage develops 30-45cm (12-18″)

Where to plant wisteria

Wisteria is often grown around entrances.
Image: SpiffyStephie

Location is in important factor to consider when growing wisterias. They’re long-lived and form woody stems which require significant support. This makes them very difficult to move if you change your mind in a few years time. They also require regular pruning to keep them under control and to encourage flowering, so it’s well worth taking your time to choose the best possible location for your plant.

Grow wisterias in a sunny or semi-shaded site in any moist, well drained soil. Wisteria flower buds can be damaged by hard spring frosts so choose a sheltered position if possible.

How to plant wisteria

Wisteria does well when trained.
Image: Debu55y

The ideal way to grow wisterias against a wall is to train them as an espalier, with horizontal support wires (3mm galvanised steel) set 45cm (18″) apart. Alternatively, you can train them onto a sturdy pergola, or even onto a tree. Supports are best put in place before planting as it will be much harder to install them once the wisteria is in the ground.

Plant your wisteria in autumn or spring. Prior to planting, add plenty of well-rotted manure or garden compost to the soil to improve its fertility and drainage. It’s vital to take the time to create ideal soil conditions for your wisteria from the very beginning, because you’ll be living with the plant for very long time.

When planting out your wisteria, use the depth that it was planted in the pot as your guide. If you’re planting a bare-root wisteria then look for a soil mark towards the base of the stem which indicates the depth to which it was planted in the ground at the nursery. This is usually found a little below the graft point – a bulge in the stem where the main plant is grafted to the rootstock.

How to look after wisteria

A well cared for wisteria will reward you with a fine display of scented blooms.
Image: Alena.Kravchenko

During their first year, wisterias benefit from regular watering to help the roots establish. Once established, wisteria should only need supplementary water during dry periods. You may wish to apply a high potash feed during the spring to encourage flower production, but don’t overdo it because overfeeding can result in more foliage and fewer flowers.

Why isn’t my wisteria flowering

If your wisteria is grown from seed it can take up to two decades to flower.
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The answer to this, one of the most frequently-asked gardening questions we receive, usually lies in one of the following explanations.

  1. Pruning. Wisterias need pruning twice a year in July/August and again in February. Check the diagram below to make sure you’re using the right technique.
  2. Seed-raised plants. Wisterias grown from seed can take up to 20 years to flower, however these are quite unusual. Nonetheless, it’s worth checking the base of your plant’s stem for signs of a graft in order to eliminate this as a possible cause of flower failure.
  3. Watering. Wisterias often thrive on neglect, but they do appreciate some extra water between July and September. This is when the buds are formed for next year’s flowers. If they run short of water during these months this can reduce your display the following summer.
  4. Frost. Spring frosts can sometimes cause the developing buds to drop before they get a chance to open. The best way to avoid this is to plant your wisteria in a sheltered spot.

How to prune wisteria

Wisteria is often used as a spectacular centrepiece by landscape designers.
Image: Puffin’s Pictures

Just the thought of wisteria pruning sends some gardeners into a panic, but it’s really not difficult once you understand a few basic principles.

Unlike many plants, wisteria needs to be pruned twice a year – once in late winter (February) to prepare the flowering spurs for the coming season, and again in mid-summer (July to August). Summer pruning controls those long, whippy shoots that are heading off into the distance, and encourages them to become flowering spurs instead.

During the first two years, the aim of pruning is to train wisteria to create a framework of permanent stems. This involves selecting and tying-in specific main shoots to the supporting wires and cutting back any unwanted growth. After two or three years, the plants will build up a strong branching habit which forms the ‘skeleton’ of your wisteria.

Wisteria growing guide

Now you have the basics of growing wisteria, we really hope you’ll feel confident to give it a go. But do remember, while correct training and pruning of wisteria definitely encourages better flowering, these plants are surprisingly forgiving.

Nothing rivals the beauty of a wisteria arbor in full bloom, but, unfortunately, successfully growing these lovely vines eludes many Midwestern gardeners.

Two types of wisteria are most commonly planted in our area: Japanese wisteria ( Wisteria floribunda ) and Chinese wisteria ( Wisteria sinensis).

Japanese wisteria is known for its fragrant violet blossoms, which are borne in 8- to 20-inch-long clusters. The individual flowers of a cluster open gradually, beginning at the base.

Chinese wisteria clusters are generally less than 12 inches long, and its individual blooms are slightly larger. Also, the flowers of a cluster tend to all open at the same time. Chinese wisteria is not quite as hardy as the Japanese and also is not as fragrant. There are cultivars of both species that have white blossoms.

Wisteria is a rather vigorous, twining vine and, in fact, can be quite invasive in some areas. The vines require strong support to keep up with their fast growth. Wisteria can grow up to 10 feet a year, especially once it’s established in the proper environment. It performs best in deep, moist, but well-drained soils that are neutral to slightly alkaline.

Since most gardeners are drawn to this plant for its blossoms, they are quite frustrated by the plant’s notorious tendency to produce only vegetation. There are many potential explanations for this annoying problem, including the plant’s immaturity, too much nitrogen, insufficient phosphorus, poor-quality plants and too much shade.

Asian wisterias need to reach a degree of maturity before they are able to produce flowers. In fact, in can take up to 15 years or more before the vines reach blooming stage.

Those who have succeeded in raising wisteria often recommend root pruning, applying superphosphate, rigorous pruning of the shoots and planting in full sun. Most important, you should start with good-quality plants that have been propagated from cuttings of plants known to flower while relatively young. If you know someone willing to share a great specimen, take cuttings of the stem tips in July. Avoid planting seedling vines because the genetic variability of seed reproduction makes it impossible to predict their blooming habit.

These vines produce their flowers on last year’s wood in mid- to late May, so wait until late spring or early summer to prune the vine. Severe pruning is often recommended, back to three or four buds, to keep the plant manageable and renewed.

There are a couple of native wisteria species that are a bit more “tame” than their Asian relatives. These native species bloom on current season’s growth and reach flowering age sooner than the Asian species. They flower a little later in spring but periodically rebloom through the summer.

American wisteria (W. frutescens) can reach 20-30 feet and bears its flowers in short, condensed clusters about 4-6 inches long. ‘Amethyst Falls’, the most common cultivar available, features fragrant, lavender-blue flowers. ‘Nivea’ is less fragrant but has longer clusters of white blooms.

Kentucky wisteria ( W. macrostachys) reaches 15-25 feet and has 8-12-inch-long flower clusters that are packed tight with blooms. Some consider this to be a sub-species of American wisteria. The cultivar ‘Blue Moon’ is a hardy selection from Minnesota with wonderfully fragrant blossoms that first appear in June and repeat through the summer. ‘Aunt Dee’ has pale lavender blooms and ‘Clara Mack’ has white blooms.

In much of garden literature, you will find claims that the American hybrids are less tenacious or less inclined to bloom repeatedly. However, ‘less tenacious’ is a very relative term. After all, we’re still dealing with wisteria; healthy specimens can grow five to ten feet in a single season. As for flowering, under ideal growing conditions, and with the correct species for your climate, you will typically get a large flush of spring flowers and often another flush later in summer (usually at about thirty percent of the volume of the spring bloom).

A well-established wisteria should be in its bloom cycle in April/May here in the Northwest, with Chinese varieties blooming prior to leaf-out and American and Japanese varieties blooming after leaf-out and slightly after Chinese cultivars. Very well-tended wisterias will sometimes bloom at other times during the growing seasons, but never to the magnitude seen in spring.

Some of you may be shaking your heads thinking: mine has never even bloomed once! This is certainly possible and may be related to one of the following issues:

  • High-nitrogen fertilizers: If your plant is near a fertilized lawn or if you use a very high-nitrogen fertilizer (strength of nitrogen, phosphorous and potassium (N-P-K) is listed numerically on packages, with nitrogen being the first number), you will be pushing a high degree of vegetative growth at the sacrifice of flowering. Wisteria is a member of the legume/pea family and as such may have some nitrogen-fixing properties, further compounding the fertilizer factor.
  • Light: While wisteria can be grown in part-shade environments, flowering requires at least six hours of sunlight.
  • Frost: As with many spring-flowering plants, a cold snap or frost can damage and kill flowers or their buds.
  • Pests and Disease: This is very unusual. The biggest pest is wisteria scale, which is not a very big problem here in the Pacific Northwest. I’ve seen only one case of wisteria scale brought into Swansons. Treatment is best done through systemic insecticides because, given the size of wisteria plants and the density of the foliage, foliar applications are often inadequate. Sometimes root rot or graft failure can occur if wisteria is planted very poorly or grown in excessively wet locations with poor drainage.
  • Water: Wisteria prefer moist, fertile, well-drained soils. Thus, given our drier Mediterranean summers, some degree of irrigation can help, especially if the plant is in a particularly dry area.
  • Pruning: While wisterias are famous for tolerating all sorts of aggressive pruning, poorly timed or poorly done pruning can greatly mitigate flowering.
  • Maturation: Plants are usually said be “adults” once they’ve reached the capacity for flowering. For some plants this can be in a single season, or it can take decades. Wisteria grown from seed can take 20 years to bloom. Fortunately, this is very uncommon in the nursery trade. The plants we see, particularly hybrids and cultivars, are grafted or grown from rooted cuttings and will bloom quite young, at around 7 years old.

If you planted wisteria this year (or even a few years ago) and it didn’t bloom, don’t worry too much. Wisteria can take time to become established and consistently put out its spectacular flower show. Very young plants may need up to 7 years before they flower freely. I have, however, come across accounts of plants flowering the first year of planting. Fortunately, growers typically make the plants available to us when they are 4-8 years old so you won’t have to wait long for blooms once properly planted.

However, if you’ve got an older plant that refuses to flower, or flowers only sporadically (i.e. once every few years), there are several things you can do to provoke flowering the next year.

I’ll start with the basics: fertilizers and root pruning. In the second part of this series, I’ll go into pruning, which is far and above the best method to promote re-blooming.

Fertilizing

The N-P-K reading on fertilizers indicates the levels of nitrogen, phosphorous and potassium they contain. Nitrogen is used primarily for the production of vegetative growth. Phosphorous and potassium are used for a wealth of plant functions, but are often understood to be tied to flower development.

Note: it is misleading to say, “Phosphorous makes flowers.” It alone does not; instead bloom formulas or superphosphate fertilizers essentially deny a plant a dose of nitrogen and shift growth from vegetative to flowering.

Give wisteria too high a dose of nitrogen – say if it’s catching fertilizer you broadcast onto your lawn (lawn fertilizers are typically quite high in nitrogen) – and flower production will suffer, but vegetative growth will be prolific.

Sometimes giving wisteria a bloom fertilizer – a generic term for any fertilizer high in P-K but low in N – can help provoke bloom, or create a fuller bloom. This should be done in early spring.

Repeatedly feeding an established wisteria is not recommended. Oftentimes, for established plants or reluctant bloomers, a healthy dose of stress helps to induce flowering.

Root Pruning

Sometimes flowering plants and trees simply languish and the reasons are mysterious or unclear. If you are having trouble deducing a cause, root pruning may sufficiently shock a wisteria into bloom.

Fear not! This does not involve digging up your plant, which is a great thing because wisteria does not transplant well, particularly later in its life.

Root pruning is best done in late fall or early spring. This technique puts the plant through a mild degree of shock, ideally provoking enhanced performance.

The best place to start root pruning is anywhere two feet away from the trunk. Drive a spade or shovel straight into the soil; you’ll want to penetrate at least one foot deep. Cleanly remove the blade, move the spade roughly 14 – 18 inches to the left or right and push it in again, making sure to maintain a distance of two feet from the trunk. With your first circle made, move out another 18 inches and start in a space where you didn’t go into the ground the first time – continue this staggering method to create roughly five concentric circles around the base, assuming you have a well established wisteria.

While not an ideal approach, this method can certainly be employed on troublesome plants. Don’t worry about harming the wisteria. Provided it is in good health, its highly vigorous nature will certainly help it continue to thrive even if you resort to this option.

Stay tuned for part 2 of our wisteria tutorial: Promoting Wisteria Bloom, Part 2: A 3-Year Plan.

Why won’t a reluctant wisteria bloom? There are lots of possible reasons. Bad attitude, for one. This is a vine that wants its way in the garden. Show it who’s boss–and persuade it to flower–with proper care. And prune it hard.

Despite its reputation as an invasive bully in the garden, wisteria can be finicky when it comes to performing. Buy a named variety from the nursery (rather than generic rootstock). The two most common types of Wisteria–sinensis (Chinese) and frutescens (native to American)–have varieties with blue, white, or purple flowers.

Here’s how to get your wisteria vine to flower:

Photography by Britt Willoughby Dyer.

Roll Out a Welcome Mat

Above: Plant wisteria in a protected, warm spot in full sunlight (try to get this right the first time, because it does not like to be transplanted).

Persistence Pays Off

Above: Whether you want a tree or a vine, you should prune wisteria each year to encourage it to bloom. And be patient: it can take two or three years of pruning to prompt it to bloom.

Survival Instincts

Above: Wisteria wants to bloom when it feels increased warmth from direct sunlight and when there is nothing above to climb.

Try to understand wisteria’s mentality. “Wisteria evolved where success lay in grappling up through a shaded canopy, putting lots of energy into climbing but none into blooming until it reached full sun and ‘knew’ it was at the top. There, both physical and chemical cues tell the vine ‘this is it,’” says wisteria expert Janet Macunovich of Garden A to Z.

“Choose a point that is ‘top’, train the vine to lay horizontally there and repeatedly clip off side branches that try to continue up,” says Macunovich. “This allows the top growth to develop in horizontal position and without shading foliage above.”

Mark Your Calendar

Above: Prune wisteria twice a season: in early March before it blooms and again in late summer to remove what Macunovich refers to as “whippy new growth.”

Early spring before leaves appear is the time to hard-prune wisteria. On a new plant, choose a sturdy vertical-growing vine to be the leader and remove other vertical vines. You can train the leader against a trellis if you are growing a vine or stake it if you are growing a tree.

The Mechanics

Above: On the leader, encourage horizontal branching. Remove suckers (new growth that appears in the crotch of two branches.

Encourage side branches spaced every 18 inches or so to grow horizontally from the leader. Hard-prune the vine in early spring and then cut off the season’s tangly new growth in late summer.

For more on wisteria, see:

  • Wisteria: A Dangerous Beauty (Are You Tempted?)
  • Paris in London: Neisha Crosland’s Planting Scheme.
  • Wisteria: A Field Guide.
  • Garden Design 101: Vines & Climbers.

Finally, get more ideas on how to successfully plant, grow, and care for wisteria with our Wisteria: A Field Guide.

Finally, get more ideas on how to plant, grow, and care for various vines and climbers with our Vines & Climbers: A Field Guide.

How to get Wisteria to bloom. – Knowledgebase Question

I know how disappointing it is when wisteria won’t bloom. There are actually three different species of vining wisteria that have similar blooms: Japanese wisteria is Wisteria floribunda, Chinese wisteria is Wisteria sinensis and American wisteria is Wisteria frutescens. The most commonly grown plant is the Japanese wisteria. All three of the plants are prolific vine producers and can grow thirty feet or more. Japanese variety blooms first–typically April, while the Chinese blooms in May and the American variety blooms June to August on the current season’s growth. For that reason, you need to prune at the correct time for the type of wisteria you’re growing. The oriental varieties set their flower buds in the fall for spring bloom and should be pruned after flowering. The American variety should be pruned hard before growth begins. All will perform best in full sunlight, and need little in the way of nitrogen, since rapid growth can preclude flowers. Wisteria can take up to 8 years to begin blooming if it is grown from seed. Age might be a factor with your plant. Nitrogen fertilizer or rich soil can also produce foliage growth to the exclusion of flowers. Try avoiding nitrogen around it, and apply some super phosphate instead. You can certainly try root pruning; it sometimes stresses a plant just enough to convince it to bloom. In this case, I hope so! Best wishes with your wisteria!

Flowering Wisteria

There are some steps you take to encourage a reluctant wisteria to bloom. A heavy application of superphosphate (0-20-0), three to five pounds per thousand square feet, can promote blooms the following season. Another trick is root prune wisteria in late fall. Root pruning is just what it sounds like – cut an edge around the circumference of the vine’s root system as though you were going to dig it up, but leave it in the ground. This practice alters the balance of nitrogen to carbohydrates in the plant. Do not dig too close to the trunk – stay about two feet away from it. Finally, severely pruning the new growth in late spring or early summer can also change the balance of nutrients in the plant to favor flowering over rampant vegetative growth.

Reasons your wisteria fails to bloom:

  • Not enough sun – Wisteria requires full sun to bloom well.

  • Excessive nitrogen fertilization that stimulates vegetative growth at the expense of flowering.

  • Heavy winter or spring pruning that also stimulates vegetative growth at the expense of flowering.

  • Improper pruning that removes flower buds (Wisteria sets its flower buds the season before)

  • Unusually severe winter weather that kills flower buds.

FERTILIZATION: If changing cultural practices still does not result in a flowering vine, apply three to five pounds of superphosphate (0-20-0) in early spring. A heavy phosphorous application has been known to stimulate flower bud formation.

ROOT PRUNING: Another strategy to encourage flowering is to root prune wisteria in September. Simply push your spade into the soil the full length of the blade all the way around the base of the plant, three to four feet away from the trunk. You aren’t digging it up, just threatening it.

TRIMMING WISTERIA: You should also prune extremely long and vigorously growing stems in late spring. This helps keep the vine in check and promotes flowering on established plants.

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