The Mimosa (Acacia in Latin), is a tree instantly recognisable by its winter flowering, bursting into thousands of bright yellow pompons. Native to Australia for most varieties, the Mimosa has inherited from its distant origins a sensitivity to cold, making it best suited to gardens with a mild climate, where frost is neither intense (no lower than -8°/-10°C at coldest) nor prolonged. Acacia retinodes or Four Seasons Mimosa which flowers from January with repeat blooms almost year-round from May to November, Acacia dealbata commonly called Winter Mimosa or Florist's Mimosa... the different varieties require little maintenance to flower abundantly.
Nevertheless Mimosas may need pruning to maintain a beautiful habit and remain just as floriferous. Discover everything you need to know to prune them perfectly.
pruning mimosa acacia dealbata retinoides

A winter wonder, the Mimosa may need pruning to maintain its beautiful shape and flower even more

When to prune mimosa?

As Mimosa flowers in winter, pruning should wait until after flowering and frost risks have passed, around March or April. The Four Seasons Mimosa is also pruned at this time.

pruning mimosa acacia dealbata retinoides

Wait until flowering finishes before pruning your Mimosa

Why prune mimosa?

Pruning Mimosa helps maintain a dense habit and promotes abundant flowering by multiplying floriferous shoots. It also removes spent flowers. This can help reduce wind resistance if needed and control the tree's size if it becomes too large for its location.

Also read our advice in Why isn't my mimosa flowering?

How to prune mimosa?

Required tools

To prune your mimosa, you will need:

All pruning tools should be sharp and clean to avoid spreading diseases between plants.

pruning mimosa acacia dealbata retinoides

Sharp secateurs, loppers and shears will allow you to prune your Mimosa properly

Maintenance pruning: for a beautiful shape

  • With shears or secateurs, trim shoot tips to round the tree's silhouette and reduce its volume if needed. Respect its natural shape, except for specially shaped trees (e.g. standard ball shapes)
  • Shorten branches by about one third of their length. You can remove up to half of the least floriferous shoots. Remember to cut just above a leaf to encourage new shoots from the axil
  • Remove dead wood, as well as branches that unbalance the shape
  • Cut back suckers growing from the base.
pruning mimosa acacia dealbata retinoides

Remove about 1/3 of shoots for maintenance pruning

Hard pruning an ageing tree: for rejuvenation

Hard pruning may be needed for an ageing, unbalanced, damaged or oversized mimosa. This involves removing all old shoots, as well as dead or damaged branches.

→ Note: Acacia retinodes or Four Seasons Mimosa does not tolerate hard pruning well!

  • For thick branches, prune just above a shoot which will act as a sap drawer and help the tree regrow. Always cut at an angle, not horizontally, and remove branches close to the trunk without damaging its bark
  • Remove dead wood
  • Cut back suckers from the base
pruning mimosa acacia dealbata retinoides

Hard pruning can for example control a tree planted too close to buildings

→ Sophie's tip: very polluting, burning green waste is prohibited. Ideally invest in a garden shredder to use pruning waste as mulch. Otherwise, dispose of it at a recycling centre!

Final precautions

  • Always clean with soapy water then disinfect with alcohol your pruning tools before and after use to avoid disease transmission. Sharpen, dry and oil them after cleaning to prevent rust and seizing: your tools will stay like new for years

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