Q&A: When do I prune my hydrangeas?

Red hydrangea
Q. When do I prune my hydrangeas?

A. I’m assuming you have Hydrangea macrophylla, either a mophead variety (as shown above) or a lacecap variety (which has flattened heads). These are the two most commonly grown hydrangeas in our backyards.

Pruning of mophead hydrangeas is often a matter of choice. Some gardeners like to prune in autumn (usually in warmer areas) to tidy their plants after flowering. Others prefer to prune in spring (best in frost-prone areas). Some just snip off the flower heads, and some don’t prune at all. In fact, macrophyllas don’t need pruning unless they’re old, large or becoming straggly. However, to keep them looking neat and tidy, most people give their plants a light snip each year. Gardeners in cooler areas should wait until spring when all danger of frost has past. Leave the spent flower heads on the plant too, if you can bear it, because the flower heads act as insulation and protect the plants and young buds from cold weather.

The important thing to remember with macrophyllas is that they flower on the previous year’s stems, so if you trim them right down to the ground you won’t get any flowers the next season. Trim off straggly growth, leaving behind as many of the fatter buds as possible. On established bushes, cut a few of the older stems down to the ground to reduce overcrowding.

Lacecaps are the same, except in warmer areas it’s best to snip off the flower heads once they’ve faded to stop plants putting their energy into producing seeds. In cooler areas, lacecaps are less inclined to produce seeds. Mopheads are sterile so they don’t produce seeds anyway. Jane

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