When to Prune Lilacs

Q: My lilacs are overgrown and need to be pruned back. When is the best time to do this?

A: For spring flowering shrubs that flower before Memorial Day, pruning should wait until after flowering. They can be pruned earlier than that if you have no choice, but you will be sacrificing this spring’s flowers in the process. This would include shrubs like lilac, forsythia, quince, pussy willow, mock orange, most viburnums and spring blooming spireas.

Flowering shrubs that flower after memorial day should be pruned by the end of this month. This would include Rose of Sharon, hydrangeas, summer flowering spireas and butterfly bush.

Regardless of the flowering time, it is always important to remove dead, broken and diseased wood whenever it is noticed, regardless of the time of year.

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 Read our Q & As with Keith Funk answering common Colorado gardening questions here. You can also hear him on the Garden Wise Radio Show