Rhododendrons, like azaleas, are low-maintenance bushes, which is particularly appreciated about them, aside from their spectacular spring flowering of course! While these bushes don't particularly like pruning, it can still be done on some older specimens, but also, and most importantly, at the level of their inflorescences.

This tutorial explains when and how to prune a rhododendron to encourage its growth and flowering.

What should you prune on a rhododendron?

We need to distinguish two types of pruning when discussing this technique for rhododendrons: pruning the branches and pruning or rather cleaning up the inflorescences after flowering.

  • Pruning dead wood on mature rhododendrons or specimens with overcrowded or diseased branches helps to balance their shape.
  • Pruning spent inflorescences prevents unnecessary exhaustion of the bush which would otherwise produce seeds, and properly encourages the growth of new flowers that will also densify the bush.

N.B.: if a rhododendron has become too large for its space, it's preferable to transplant it elsewhere rather than prune it, as these bushes grow slowly and we adore their majestic presence after several years of patience!

to prune or not rhododendron

When to prune a rhododendron?

  • For flower pruning, intervene when they have faded, in late May or June-July for later varieties, as the underlying buds become larger as the weeks pass.
  • For branch pruning, on mature rhododendrons or specimens with poorly positioned branches, proceed around May or June, just after flowering.
pruning old rhododendron

How to prune a rhododendron?

Inflorescence pruning

The future buds are located right at the base of the flower spikes. Wait until they appear (they have a characteristic pointed shape) to spare them when pruning spent flowers.
Gently take hold of the entire spent flower spike, twisting it to one side just above the buds to avoid damaging them. Use snips or fine secateurs if you're worried about harming the buds, cutting right at the base of the four to five already formed and clearly visible buds.

pruning pinching rhododendron flowers

Branch pruning

The pruning operation is kept to a minimum for branches and the overall structure. Only prune dead wood, which may have formed over the years, as well as obstructive branches on a pathway for example. This is just a very light refresh of young branches, without cutting old wood which would struggle to regrow, to maintain a balanced and airy habit.
You can also, if you wish to maintain a very rounded shape, cut juvenile shoots at the top, always taking care to identify buds and pruning with secateurs just above them.

My advice: with rhododendrons, carefully choose a species and variety by always assessing its mature size. As mentioned earlier, rhododendrons grow slowly and it's interesting to preserve their habit and sublime appearance by not pruning them.