There are quite a few reasons your Wisteria may not be flowering, from the variety of the plant itself, through to its location and growing conditions to how you’re treating it. A couple of the most common reasons we see that cause a loss of flowers are, firstly, you have pruned it incorrectly and removed the flowering shoots, and secondly, you are either feeding it too much or providing them with too much nitrogen in the soil. Ideally, you should feed them phosphate fertiliser to encourage flowering.

To learn more about these issues in more detail, as well as other reasons your Wisteria may not have flowered, read more below.

Incorrect pruning is a common cause of poor flowering

Check that you’re pruning your Wisteria, not only at the correct time of year but in the right way too. Pruning a Wisteria early and in the mid-summer disrupts the formation of flowers for the next growing season. You can, without realising, literally be pruning off the shoots that will produce the flowers the following year.

What to do

Read my guide on How to prune Wisteria for details on correct pruning to ensure you don’t unintentionally remove flowering shoots.

Wisteria can take years to flower, especially if they are grown from seed

Another common reason that your Wisteria may not be blooming is that it has been grown from seed or it is simply too young. Wisteria propagated from seed can take up to 20, yes 20, years to produce any flowers. That’s a really long time to wait to see any flowers. This is why most people don’t choose to grow Wisteria from seed, and why they are often grafted.

Even grafted Wisterias (the ones usually sold in garden centres) can, believe it or not, take three to four years to flower, so if you know you have correctly pruned your Wisteria, a little more patience may be needed.

What to do

If you have grown a Wisteria from seed, put it aside for the long wait and purchase another plant propagated from a cutting or a graft instead. Better to enjoy the flowers before retirement!

Wisterias need full sun, plants in the shade will grow but will struggle to flower

Wisteria love to be planted in sites where they have access to full sun, but they do grow in partial shade. This is deceptive as the plants look happy to be in the shade, however, they won’t produce as many flowers as they would if they were in a sunny spot. There are also lots of different types of ‘shade’ dappled shade, shade in the afternoon. You get the point!

What to do

Try to create a sunlit area around your Wisteria. Cut down any encroaching plants and remove any tall temporary structures if possible. Ideally, they need to be planted in full sun so ideal on the south- and west-facing walls.

Spring frosts

If your Wisteria is hit by spring frosts, the developing buds can become distorted or damaged. They may fall from the plant before the flowers have a chance to develop. This is usually rare but it has been known to happen.

What to do

Protect your Wisteria plants in the winter and spring if it’s small enough. Don’t cut back the foliage in the autumn. Use horticultural fleece if necessary to wrap around the plant. Take this advice loosely as it’s not practical for most people, but can be done for those growing smaller, standard wisterias.

Lack of or too much of one nutrient

I touched on this already in the introduction. The lack of nutrients applies particularly to potassium that’s needed for flower formation. In addition or alternatively, the soil may have too much nitrogen which promotes foliage growth instead of bloom development. This can also be caused if you use a fertiliser high in nitrogen because this will encourage your Wisteria to produce lots of leafy green growth instead of a balance of both leaf and flower.

What to do

Apply a fertiliser rich in potash in the spring to help along the bloom development. Tomato fertiliser applied once a month over the summer is perfect.

Lack of water

Wisterias need to be watered well in dry spells. A lack of water between July and September slows down the bud formation for the flowers of the following season. This is also the case for Wisteria grown in pots, they need regular watering because if they are allowed to become dry when the buds are forming, this again, can lead to no flowers.

What to do

Pay particular attention during dry spells to your watering schedule. Increase watering if needed.

Pigeons or mice

Look out for teeth marks on your flowers. The flowers may also appear shredded, this damage is often caused by pigeons or mice.

What to do

Discourage pigeons and mice from your garden. This is not an easy task, so you may have to live with the loss of some flowers to these pests.

I also have a guide that includes other common Wisteria problems as well as a guide on why your Wisteria might be wilting or the leaves turning yellow. I also have a guide that discusses the Wisteria scale that can lead to dieback.

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