Quote from Lee Garden Ninja on 5th March 2025, 4:38 pm

Hi @novicegardener

Thanks for your gardening question, ideally I would need you to upload a photo so I can see the Bottle Brush Plant to fully advise, but let me give you some tips to get you started when pruning these fabulous shrubs. 

Calistemon comes from Australia but are pretty tolerant of our cold winters here in the UK. Making them an excellent tropical-style shrub for any garden design as long as they are not too exposed. They need full sun to fully thrive and their bright red 'bottle brush' flowers help bring a red hot blast to any garden. Lastly, bees and insects absolutely love their pollen-packed flowers.

It sounds like you need to hard prune back parts of your Calistemon if you want to regenerate growth lower down, or consider planting herbaceous shade loving perennials at the base to help fill the gaps.

How & When to Prune Callistemon Shrubs in the UK

When calistemons have finished flowering, it's important to prune out any flowers that are spent and branches that are damaged, diseased, or crossing, which can hinder the growth of your shrub in later years. Pruning is essential to keep it healthy, encourage flowering, and maintain an attractive shape. However, knowing when and how to prune is crucial to avoid damaging the plant.

When to Prune Callistemon

The best time to prune Callistemon is immediately after flowering, typically in late summer. This allows the plant to produce fresh growth before winter without leaving it vulnerable to cold damage. Light trimming in early spring can also help shape the plant before the growing season begins.

Avoid heavy pruning in autumn, as this can stimulate tender new growth that may struggle to survive the colder months.

How to Prune Callistemon

1.Deadheading Spent Flowers – Once the flowers fade, snip them off just behind the bloom. This prevents the plant from putting energy into seed production and encourages more flowers in the next season.

2. Shaping and Light Pruning – Trim back new growth just above a leaf node to maintain a neat shape and encourage bushier growth. Avoid cutting back too hard, as Callistemon does not always regenerate well from old wood.

3. Rejuvenation Pruning – If your Callistemon has become leggy or overgrown, you can remove some of the older, woody stems to promote fresh growth. However, this should be done gradually over two to three years rather than in one severe cutback.

4. Removing Damaged or Crossing Branches – Thin out any weak, dead, or overcrowded branches to improve air circulation and reduce the risk of disease.

Additional Care Tips for UK Growers

• Callistemon thrives in full sun and well-drained soil. Poor drainage or excessive shade can weaken the plant and reduce flowering.
• Applying mulch and a balanced fertilizer in spring will help promote healthy new growth after pruning.
• In colder regions, Callistemon may need some winter protection. Mulch around the base and consider covering young plants during harsh frosts.

Do upload some pictures in reply to this and let me know how you are getting on!

All the best

Lee Garden Ninja