Pruning Hydrangeas In NZ

Hydrangea Pruning

Hydrangea pruning is easy when you have the right advice and the resulting plants in spring and summer are well worth the effort!

How Do You Prune Hydrangeas?

Hydrangeas are pruned each winter in NZ to contain growth and encourage fresh, new growth that will bear flowers. The Plant Company recommends they are pruned back to a low crown which has short stems (about 10 cm long) with at least two buds on each stem remaining using secateurs. Any dead stems should also be removed at this time, along with stems that are criss-crossing or show disease. Young plants will generally be left with five stems whereas older plants can have 20-30 stems remaining. These can be thinned back to 15 if desired which will help produce bigger flower heads. Longer stems can be left on younger plants while they are establishing. In general, the harder the plant is pruned back, the more contained it will grow the next season. Flowering can be affected with hard pruning but that is more likely to cause delayed flowering only.

A mistake often made is to not prune the plants hard enough. This error results in a woodier plant and a much larger plant that can be difficult to contain.

How Hard Can I Prune Or Cut Back A Hydrangea?

Most Hydrangea varieties will sprout new shoots when cut right back, even to stumps at ground level. However, this relies on the plant having heathy stems at the outset. If the stumps have any dead wood or they are too old (more than five years), they may not shoot or may only shoot on one side. Similarly, stumps that still have actively growing foliage may not sprout unless all the foliage connected to that stem is completely removed.

Severe pruning using a pruning saw is best undertaken any time from late autumn until early spring. Multiple shoots will usually grow from each stump and the plant may even produce flowers on the new shoots. However, Hydrangeas grown in heavy shade environments may struggle to re-establish when cut back severely.

When To Prune Hydrangeas

When to prune hydrangeas is a question frequently asked. In short, it's best to hold off pruning Hydrangeas until mid-late winter. Don't be tempted to prune too early as the pruning will stimulate new growth which could be burnt by frosts. Please refer to the section on how to prune Hydrangeas for detailed information on this activity.

Why Do You Need To Prune Hydrangeas?

Hydrangeas grow with a rounded, almost ball-like shape, with all of the new growth generally on the outside of the plant. That ball will keep getting bigger and bigger if it is not pruned back and will quickly become woody at its centre. We therefore prune to contain growth, encourage fresh foliage, and to present a more aesthetic plant. Pruning can also assist with giving larger flower heads as we are encouraging new growth that will generally result in fewer but better flowers. Please refer to the section on how to prune Hydrangeas for detailed information on this activity which is undertaken during winter.