Butterfly Bush Pruning

butterfly on Beddleia

The buddleia, because of its rampant growth makes it undesirable for some homeowners, that’s where butterfly bush pruning comes into play.

Many shrubs like the Buddleia can usually be trained or manipulated to keep the style and characteristics they were first planted for.

When we say manipulated we are referring to pruning.

Pruning can come in several forms – by the great pruner we call winter, or by you with your trusty pruning shears.

For example, in Ohio last year I saw some Buddleia Davidii which were smaller and very attractive compared to those in the south.

The difference? The northern plants were killed to the ground in the winter, returning again when spring arrived – and they looked fabulous.

Let’s look at when to prune Buddleia as there are some subtle differences in pruning depending on species.

Pruning Buddleia in Spring

Correctly pruning a butterfly bush is of great importance.

The varieties which bloom and flower in late summer and autumn, which are usually the varieties related to Buddleia Davidii, should receive a hard pruning every year in the spring.

By hard pruning we mean the growth and shoots from the previous summer’s growth should be cut all the way back to within 3 or 6 inches of the older wood.

However, if you want to increase the size of the bushes quickly, cut the summer’s growth back to about 6 to 9 inches long. Make sure you remove, cut and thin out all weak twigs.

In northern regions, winter may kill the growths to the ground. As long as the roots survive, new shoots should emerge and produce blooms the same summer, just in time for butterfly season.

Most varieties of Buddleias produce their flowers on the new shoots grown during the current year, but there are some exceptions – Buddleia alternifolia.

Buddleia Pruning After Flowering

Buddleia alternifolia is a type which loses its leaves and produces its flowers on the older wood.

Buddleia globosa, and Buddleia Colvillei the evergreen, or semievergreen species also produce blooms on their branches from the previous seasons growth.

For this reason, the flower buds need to be “preserved” and pruning should NOT BE DONE until after the flowering season has finished which is normally in June.

Pruning is slightly different. Lighting thinning and removal of old branches is done at this time. Long shoots can be shortened.

After 5 or 6 years the bushes will not be as attractive – tall and awkward looking.

The old wood will need to be pruned back hard in early April. You’ll lose blooms for one season, but new vigorous growth develop for next years bloom.

Spring Trimming of The Buddleia Butterfly Bush

Question: Should a buddleia be trimmed in the spring? Mine is about four years old and has never been trimmed. It blooms well, but the flowers are not as large as I expected. Would trimming make them larger? CC, Illinois.

Answer: Pruning butterfly bushes should improve its blooming… so do not wait another 4 years. It is best to think of the butterfly bush as a herbaceous perennial and treat it as such instead of as a shrub.

For best results – with Buddleia Davidii – and secure the best bloom from a buddleia, prune it to within about six inches of the ground each spring just at the time new growth begins to show at the base of the shrub.

When the Crocus come out is a good indicator. This new growth is usually evident in late March. New wood produced after this severe pruning is more vigorous and the flowers heavier than the ones produced on two-year-old wood of the Buddleia.

Image: Chris Potako

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