Hydrangea – Identification and Pruning

Q: I have hydrangeas on some new property. I would like to prune them but am unsure which hydrangeas I have, and therefore when to prune them. How do I tell them apart?

A: In my garden, the color and shape of the faded bloom helps me identify hydrangeas.

Common hydrangea, Hydrangea macrophylla, (the one with blue or pink flowers) flower heads fade to dark tan by the end of July,  flowers are usually globe-like, and on the tip of stiff stems. If the brown flowers are like a lace-cap, it is almost certainly a macrophylla hydrangea. The best time to prune is in July. This gives them plenty of time to grow new stems that will produce flowers next summer.

‘Annabelle’ hydrangea blooms are a very light tan, almost white and on the end of three-foot long arching canes.

‘PeeGee’ hydrangea flowers look like Hydrangea macrophylla blooms but the shrub itself is much bigger…usually 5 – 10 feet tall. Stems are very stiff and arch gently at the top.

‘Tardiva’ hydrangea flowers are strongly cone-shaped but the leaves are not oak-shaped. ‘Tardiva’ blooms in mid- to late summer, after oakleaf hydrangea.

Oakleaf hydrangea also has cone-shaped flowers but the bark of the stems peels attractively around the bottom third of the stem.

The Cobb Extension service hydrangea factsheet tells how to prune once the shrub is correctly identified.

common hydrangea (Hydrangea macrophylla) with mophead flower

common hydrangea (Hydrangea macrophylla) with mophead flower

common hydrangea (Hydrangea macrophylla) with lacecap flower

oakleaf hydrangea (Hydrangea quercifolia)

pannicle hydrangea (Hydrangea paniculata)

‘Annabelle’ hydrangea (Hydrangea arborescens)