Pruning hydrangeas

June 11, 9:50 AMSF Gardening ExaminerChris McLaughlin

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Photo by La Fattima

I asked my friend one day what happened to her beautiful hydrangea shrubs that used to be under her front window. She told me that although she adored their gorgeous flowers, she’d given up on them because hydrangeas were simply too hard to grow. It was strange because I’d remembered her lovely hydrangeas from the year before and asked her what went wrong.

She said the first year they were beautiful, but the second year there was very few blossoms and the third – none at all. My friend had decided they were too fussy and had given up. Now, here in the Bay Area, hydrangeas just aren’t all that fussy so it was fairly easy to figure out what happened.

These perennial shrubs aren’t hard to grow, but you do need to know when to prune which species. For instance, many of the hydrangeas that bloom in pink or blue belong to H. macrophylla; in which there are a few different varieties.

Some bloom on old wood and some bloom on new wood. Old wood refers to stems grown last season and have the flower buds all ready to go, whereas new wood is referring to stems that are grown in the current season. Still there other varieties that flower off of both wood types.

What that means to the gardener is that the usual dormant season pruning needs to be tailored to the species and the variety within that species. While new wood blooming hydrangeas can be pruned rather deeply late in the dormant season, most gardeners prune old wood types strategically - if at all.

Old wood types should certainly be deadheaded (removing old blooms is not pruning), but it’s suggested that the only other pruning you do to these ladies is to prune for shape or form such as weak or unwanted cross branches.

Examples of New Wood Hydrangeas:

• Hydrangea macrophylla (Bigleaf) 'Endless Summer'
• Hydrangea anomala subspecies petiolaris (Climbing Hydrangea)

Examples of Old Wood Hydrangeas:

• Hydrangea macrophylla (Bigleaf Hydrangea) – Mop Heads and Lacecaps
• Hydrangea quercifolia (Oakleaf Hydrangea)

*For more on hydrangeas see Growing hydrangeas in the Bay Area.