In stark contrast to my husband, who will happily take a hedge cutter to anything, I’m a bit of a wuss when it comes to pruning. I’m still a bit cautious with the secateurs on most shrubs, but there’s one plant that I know I can be brutal with: Buddleja davidii (the butterfly bush).
Buddleja (or Buddleia) davidii produces new growth on new wood, and will produce up to 3 metres of growth in 1 year. So, if you don’t cut it back each year you will end up with a very tall plant of old woody stems with straggly new growth on top.
Cut it back hard – now!
You can’t really over-prune it. It needs cutting back hard to about 1 foot from the ground in early Spring (now) – provided the weather is mild – before it starts producing new growth.
1. Trim back top growth with secateurs. This will make it easier to get to the lower stems near the base of the plant.
2. Cut back the thick woody stems near the bottom to 1–2 feet (30–60 cm) above the ground. You will probably need a pruning saw or lopper for this, as the stems will be pretty thick near the base of the plant.
Try to keep an open framework of 5–6 main branches. Remove any crossing branches that will rub on other stems. The Buddleja in the photo above is only a couple of years old, so there aren’t too many stems yet, but the older it gets the more stems it will produce.
If your Buddleja is very congested around the base with old dead stems, remove them completely (either to the ground or cut them off flush to the stem).
Be brave, be brutal
It seems severe, but don’t be alarmed by the way your Buddleja looks. I promise it will regrow … a lot! In fact, you’ll be amazed how quickly it starts to produce new growth.
Prune the right Buddleja in the right way
One important note here. Make sure you are pruning Buddleja davidii in this way, and not Buddleja alternifolia or Buddleja globosa. Both of these Buddleja species produce new growth on old stems, so they should never be cut back hard in the way described above.
I thought the upper stems were pretty, so instead of throwing them all away I created an end-of-winter flower arrangement. Combined with the winter stems of Sedum spectabile, it turned out to be quite striking.