Pruning hydrangeas: when, how hard and by type

How you prune a hydrangea depends on the wood on which it flowers. A mophead hydrangea flowers on last year's wood: you prune it lightly, after flowering from late August to September, by cutting away only the spent flowers and dead wood, and never hard. In winter and spring you leave it alone. Panicle hydrangea and Annabelle flower on new wood: you cut these back substantially in March, Annabelle to 30 to 50 cm above the ground and a panicle hydrangea by a third to half. You prune a climbing hydrangea lightly after flowering in July or August, a mountain hydrangea in late August.

Pruning hydrangeas by type and situation

Old wood or new wood: the rule behind everything

A mophead hydrangea forms its flower buds in autumn, at the top of the branches that have grown that year. Those buds overwinter outside and open the following summer. Anyone who cuts back such a shrub hard in spring is cutting away precisely this summer's flowers. The same applies to oakleaf, mountain and rough-leaved hydrangea and to climbing hydrangea. That is why you prune a mophead hydrangea lightly and after flowering. If you doubt which branches are dead in spring, wait until May: then you will see which ones shoot. You can read more about the right time in when to prune a mophead hydrangea.

Panicle hydrangea and Annabelle make their flowers on the shoots that grow in spring. Vigorous pruning in March gives strong stems and full flowering, as explained in when to prune a panicle hydrangea. If you do not know which you have: a mophead hydrangea has rounded or flat flower heads, a panicle hydrangea has long, pointed plumes and Annabelle has large, white balls.

Young hydrangea

In the first year after planting you prune hardly at all. Remove only dead or damaged wood, do not cut into the tips and never take away more than 10 to 20 per cent of the plant. From the second spring onwards you prune panicle hydrangea and Annabelle like a mature shrub. The complete approach by season is in pruning young hydrangea.

Mature hydrangea: annual maintenance

With a mature mophead hydrangea the work remains limited: after flowering remove the spent flowers, take out dead wood and possibly remove some of the oldest stems at the base if the shrub becomes too dense. Weak, thin branches that bear no flowers you thin out after flowering, as described in removing weak branches from hydrangea. What needs to be done after summer by type is in pruning hydrangea after flowering.

Pruning does not change the colour of a mophead hydrangea; that depends on the acidity of the soil. If you want to keep blue flowers, read keeping hydrangeas blue. Anyone who wants to give hydrangeas a place where they come into their own can first try them out in a garden design of their own garden.

Neglected or oversized hydrangea

You tackle an old, overgrown shrub in two steps: first remove all dead wood and pencil-thin branches, then the shrub itself. Panicle hydrangea and Annabelle tolerate being cut back vigorously in one go in March. For an old, overgrown shrub our guide describes one hard pruning in June, just after flowering: everything back to 60 to 80 cm, so that the shrub still grows for four to five months before winter. If you want to proceed more cautiously, spread it over two years: the first year cut back one side hard, the next year the other side. In both cases expect little flowering for one to two years; you can read how to approach this in rejuvenating old hydrangea. If your hydrangea does not flower, first check whether it has been pruned hard in spring or has had frost, as explained in hydrangea does not flower.

Frost damage, pot and hedge

After a severe winter or late frost you wait until spring to see which branches are really dead; some branches that seem dead in April still shoot in May. Then prune back to healthy, green wood, as in hydrangeas and frost damage and frozen hydrangea buds. A mophead hydrangea in a pot you cut in September or October only the spent flowers; a panicle hydrangea in a pot you cut back then to 30 to 40 cm, so that it remains compact. Prune a pot hydrangea somewhat more cautiously than in the ground and place the pot in a sheltered spot in winter: roots in a pot freeze more quickly. See pruning pot hydrangea.

For a hedge the panicle hydrangea is the best choice: you cut it back in March to the desired height and shape and again in May for neat edges. An oakleaf hydrangea grows too naturally and irregularly for a formal hedge.

Step-by-step plan

Step 1: See which hydrangea you have

Rounded or flat flower heads indicate a mophead hydrangea, long pointed plumes a panicle hydrangea, large white balls Annabelle. This step-by-step plan is for the mophead hydrangea, the most planted type.

Step 2: Wait until after flowering

Prune a mophead hydrangea when flowering is over and the clusters fade, usually late August to September. In spring you do not cut it back: then you remove this summer's flower buds.

Step 3: Cut off the spent flowers

Cut off each spent flower head, just above the first healthy buds below. Leave the rest of the branch: that is where the plant makes next year's flowers.

Step 4: Remove dead wood

Branches that are grey or black, dry and brittle you cut away to healthy wood or to the base. If in doubt, leave the branch: in May you will clearly see which branches shoot.

Step 5: Thin out a shrub that is too dense

If the shrub is very dense, saw away a few of the oldest, thickest stems at the base. Never take away more than a third of the shrub and do not shorten the rest.