Pruning rhododendron: when & how to prune correctly?

Rhododendrons enchant us with their lush flowers. But when and how do you prune them properly in order to achieve the best possible flowering?

Rhododendron (Rhododendron) can be found everywhere – in gardens, parks and even in the wild. Especially popular are the purple, pink and white flowers that attract all the attention in the spring. The evergreen shrub from the heather family (Ericaceae) usually grows well without heavy pruning. At certain times, however, appropriate maintenance pruning may still be useful. We show you what to bear in mind for perfect rhododendron pruning.

When to prune rhododendron?

The ideal time to cut rhododendron can vary. A maintenance pruning to bring the sprawling shrub back into shape is best done after flowering, starting in May and continuing into June. If the rhododendron needs to be cut back more due to internal thickening, you should do this before flowering in the autumn or spring so that nesting birds are not disturbed during pruning.

Pruning rhododendron after flowering

Light pruning after flowering is a suitable method for cutting the rhododendron into shape and removing diseased and overhanging shoots. Ideally, perform pruning immediately after flowering (May to mid-June). When pruning a rhododendron, pay attention to the following things:

• Use clean and sharp pruning shears
• Pruning takes place after the shoots emerge
• Cut at a slight angle
• Wear gloves when pruning
• Remove all diseased, injured and protruding shoots
• Do not injure already formed buds

Since the dormant buds are just below the leaf head, the cut is placed just behind it. The cut is made at an angle to allow water to better drain from the cut surface. The buds for the next year are already created immediately after flowering, so you should be especially careful. When doing topiary, try not to injure buds, if possible, so that next year you can enjoy the flowers again. This works best with a smaller pair of rose scissors. Also, make sure that your chosen gardening tool is always clean and sharp so that no diseases are transmitted, and minimal injury is caused to the shoot. However, the next flowering is not the only reason to proceed with caution: March to the end of September is breeding season for native birds, and they also like to make themselves comfortable in your rhododendron. Therefore, major pruning should be postponed until the autumn or spring. Also, rhododendrons are poisonous – so always wear gloves.

Pruning rhododendron: step-by-step

In the winter months, when the nesting season is over, heavier pruning can be done on the bush. Heavy pruning in rhododendron is carried out when:

• the plant is bald from the inside. This means more light reaches the inside again and your rhododendron grows beautifully branched and bushy.
• the plant has been incorrectly pruned over the years or has been badly damaged and needs to be brought back into shape by rejuvenation pruning.

Whether you cut back in the autumn starting in October or in the spring around February makes no difference here. There should just be no danger of frost. However, rhododendrons tolerate pruning differently. Grafted plants usually have a problem with heavy pruning, whereas non-grafted plants can tolerate pruning right into the old wood. In addition, it sometimes takes several years for the plant to grow back to its former shape. You should also not expect flowering in the first two years. If severe pruning should nevertheless become necessary at some point, the following procedure is followed:

1. Use a sharp and clean tool
2. Pruning takes place after the emergence of shoots
3. Guide the cut at a slight angle
4. Wear gloves
5. Leave at least half a metre

For information on how you should care for your rhododendron, see our dedicated article here.