Why isn't my wisteria flowering?

Specifics of growing wisteria

To understand why a plant isn’t flowering, it’s important to know its cultural requirements and whether these are being met. Wisteria, the Latin name for the genus, is a climbing plant with several origins, the most common here being the Chinese species (Wisteria sinensis) and the Japanese (Wisteria floribunda).

Each has its own characteristics, but overall they share similar needs, on these essential criteria:

• Soil: they require good garden soil, well-drained, deep and fresh, light and slightly acidic. Soil that is too compact or retains too much moisture can hinder growth and flowering.
• Exposure: Wisterias love sun! A south-facing exposure is ideal north of the Loire. A west-facing exposure is also recommended across much of the country. They tolerate a little shade or partial shade in very hot regions.
• Hardiness: all are hardy, wisterias establish themselves fairly widely across France. However, Japanese wisterias are a little more cold-sensitive. Cold winds and late frosts can affect an early bud burst period, as is the case with Chinese Wisteria.

A Wisteria floribunda or Japanese wisteria in May, in full bloom

Main reasons why wisteria does not flower

Considering the specifics of wisterias, there are several factors that greatly influence flowering induction. Here are the most common ones for wisterias:

• Not enough sun: first, you need to know whether the plant has been planted in proper conditions for flowering. If a wisteria can grow in partial shade, it will flower much more freely with warmth, and hence sun. Location is clearly the key factor for achieving generous flowering in wisterias. Beyond this exposure aspect, a site sheltered from prevailing winds is essential.
• Improper pruning: pruning at the wrong time often compromises flowering in shrubs or climbers. For wisteria, pruning in late winter (February) is recommended to stimulate flowering (cut back to two or three buds). But as Chinese wisteria is repeat-flowering (it flowers again later in summer, twice or even three times), pruning carried out at the end of the first flowering, followed by a second in summer, helps stimulate the climber again, which will produce new flowers (although less fragrant and fewer in number than the spring flowering on bare wood). To read: How to train and prune a wisteria? and When and how to prune a wisteria?

Severely pruned at the right time, wisteria quickly produces a plentiful number of flowers

• A plant grown from seed: if you have grown a wisteria from seed, it is normal that the plant will not flower for about ten years, and in all cases these wisterias will have a less generous flowering than varieties grafted or layered from a mother plant.
• Soil: a soil that is too rich can favour leaf growth at the expense of flowers.
• Damage or stress: stress due to a lack of water, a recent transplanting, or damage caused by parasites can delay flowering.

The flower buds of Chinese wisteria (Wisteria sinensis) are very sensitive to frosts

• A plant grown from seed : if you have grown a wisteria from seed, it is normal that the plant will not flower for about ten years, and in all cases these wisterias will have a less generous flowering than varieties grafted or layered from a mother plant.
• Soil : a soil that is too rich can favour leaf growth at the expense of flowers.
• Damage or stress : stress due to a lack of water, a recent transplanting or damage caused by parasites can delay flowering.

A few tips to boost flowering

By understanding the specific needs of wisteria and adjusting your gardening practices accordingly, you will increase your chances of seeing this spectacular climbing plant flower abundantly.

Here are our tips for achieving a beautiful and long-lasting flowering of your wisteria:

• Prune regularly : prune your wisteria in winter to shorten shoots and stimulate the formation of flower buds. A second, or even third prune in summer (pinching) is really beneficial for Chinese wisteria and American wisterias (Wisteria frutescens).
• Protect your plant : make sure your wisteria is sheltered from strong winds and late spring frosts, which can damage the flower buds.
• Improve the soil : if your wisteria is planted in soil that’s too rich, avoid fertilising it, especially with nitrogen fertilisers, which can reduce flowering. A tip tested by Virginie D.: ‘an ash top-dress at the base of the wisteria in late winter, about a shovel-full of ash, lightly raked into the surface, has allowed her wisteria to flower as if by magic’!
• Water stress : a light water stress at the start of the season can encourage the wisteria to flower. This means reducing watering so that the plant concentrates on flower production rather than leaves.
• Patience : if your wisteria is young, give it time to develop. Moreover, if it was grown from seed, it may take several years before it starts to flower.
• And of course, give it more sun if grown in a pot!

A late February prune helps produce floriferous flower buds