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Pruning butterfly bush: When and how should gardeners prune for both types of the perennial?

We all know how important pruning shrubs and trees. This process not only improves the appearance of these plants, but also fixes damaged areas and prevents them from getting out of control. While it is said that improper pruning leads to weakened or damaged plants, this is not the case with the popular butterfly bush. Pruning butterfly bushes is easy. These perennials are extremely hardy and adaptable. Their blooms are a beautiful addition to any garden. But to keep them blooming so beautifully, you need to know how to prune butterfly bushes.

Types of butterfly bushes

But to keep them blooming so beautifully, you need to know how to prune butterfly bushes

There are two types of butterfly bushes: Buddleia davidii and Buddleia alternifolia. Buddleia davidii is a deciduous shrub with dark purple flowers that bloom from June to September.  Buddleia alternifolia is a deciduous shrub with light purple flowers in spring. This type of butterfly bush blooms on the previous year’s shoots, so annual pruning is not an option.

How you prune your butterfly bush depends on the type of shrub you have

Watch for dieback. Dieback is caused by severe winters or disease. In this case, a particularly cold winter could be the cause of your butterfly bush dieback. When a plant dies, the leaf tips or roots begin to die, slowly leading to reverse dieback that ends with the entire plant dying. Dieback is common in butterfly bushes in colder climates – in very cold winters, butterfly bushes often die back to their roots. However, that doesn’t mean they can’t be saved – that’s what pruning is for. Butterfly bushes break winter dormancy late, so you don’t have to watch for winter damage as the plant may still be dormant.

How to prune the bush

Pruning butterfly bush - When and how gardeners should prune for both types of the shrub

How you prune your butterfly bush depends on the type of shrub you are planting. If you have a Buddleia davidii, prune it back with a hard cut. Because they often die back in the winter, this type of butterfly bush can tolerate – and often needs – heavy pruning. Even if your butterfly bush doesn’t die in winter, prune it in late winter to a height of 15 to 20 inches above the ground to ensure good growth the following spring. If you have a Buddleia alternifolia, prune the shrub heavily to about ⅓ of its size immediately after flowering in early summer. Base your pruning on the shape of the shrub.

Butterfly lilacs do not need to be pruned every year.


You can prune the shrub back to twelve to twenty-four inches in height. For most plants, this is a drastic reduction. But these plants not only tolerate it, but are often better off for it. This way, some of last year’s growth is retained, allowing this area of the garden to fill in more quickly and produce many flowers. If the leaves have already sprouted, you can still cut them back a bit, but if you cut below the new shoots, it will take much longer for them to fill in this year. A fertilizer application in March or April and another in June or July will encourage growth. A generous portion of compost or organic general purpose fertilizer is recommended.

If your butterfly bush is in the back of the garden against a fence and you want it to grow taller, cut it back to about three feet so that the plant will grow taller (and thus flower) shoots. You can then grow lower plants near the butterfly bush without neglecting its flowers.

Cut back your Buddleia davidii in early spring or late winter

When to cut butterfly bush

Generally, in warmer climates, butterfly bush should be pruned during the winter months when the plant is dormant. However, butterfly bush can be pruned in the spring without any negative effects. Just be sure to wait until the danger of frost has passed. Keep in mind that if you prune your butterfly bush, an extra layer of mulch may be needed around the shrub to insulate it, especially in colder climates.

In warmer climates, this is not necessary except for aesthetic reasons, as the butterfly bush usually stays green. Those who choose to prune in the spring or even summer need not worry, as these shrubs handle stress well and come back stronger than ever. Butterfly bushes grow quickly and respond well to pruning. New growth and flowers should reappear within a few weeks of pruning.

Pruning butterfly bushes is simple


Prune back your Buddleia davidii in early spring or late winter. It is best to prune the plant before new growth begins in the spring. In climates with cold winters, the plant will most likely die back completely. However, avoid pruning in early winter. This is because the stems are hollow and water that accumulates in the trunk and then freezes will cause the wood to split. This is not a good thing. Butterfly lilacs bloom on new wood.

So as long as you have plenty of sunlight, you will have plenty of blooms throughout the summer if you prune in the spring. Butterfly lilacs don’t need to be pruned every year. They only need to be pruned when they grow too large for their allotted space. However, since these perennials only bloom on new growth, many gardeners cut them back heavily in the spring to encourage strong new growth and lots of blooms.

Remove faded flowers

Cut off the faded flowers while the plant is in bloom

You should cut butterfly bush flowers when they have faded , as long as the plant is in bloom. This means you should pick or cut off the dead flowers while the shrub is still blooming. Faded flowers start to turn brown and look very wilted. Cut the dead flowers back to their base on the stem. This will ensure that your shrub will produce new flower buds longer into the blooming season than if left unattended. At the end of the season, you should cut off any spent flowers. This will help the plant form buds for the next year. It also reduces the likelihood that the butterfly bush will self-seed, taking over the entire garden.