May is when the gardening season begins in earnest here in the Shenandoah Valley and in many other locations across the country. The days have become longer and warmer and even the nighttime temperatures have warmed up.
Get your shears ready! It is (or will soon be) time to prune your spring blooming shrubs like forsythia, lilacs, azaleas, and rhododendron.
These shrubs will soon be producing the buds for next year's flowers. If you wait until fall or even in mid-summer to prune, you will be cutting off all these flower buds!
Spring blooming shrubs should be pruned right after they finish blooming. Here are some different pruning methods for these shrubs:
- Pruning spent flowers. After the flowers on your spring blooming shrubs have faded, remove the old flowers. This prevents seed formation which can reduce the bloom for the following spring. For azaleas, you can remove about 2"-3" of the branch tips when you shear off the old blooms. With rhododendrons, carefully remove just the dead flower clusters because the new leaf buds are found right behind them. Prune off the spent flower trusses of lilacs just above the first leaves beneath the old blooms.
- Pruning and thinning to shape your shrub. Thinning will allow more light to reach the the interior of the shrub. This can lead to a greater production of flower buds the following season. This is especially important for lilacs and forsythia. Thinning can also reduce disease problems such as powdery mildew because it increases air circulation and lowers humidity. Cut several of the oldest stems back to the ground but do not remove more than 20% of the growth. Prune out any crossing branches or wayward stems. Older lilacs can be pruned into small trees by removing all but one or two of the thickest stems and pruning out the lower side branches.
See the photo above.
- Pruning to reduce size. If your shrubs have become too large for their space, you may need to do some more drastic pruning. One of the best ways to accomplish this is to cut about a third of the oldest stems/branches back to a height that is about 12" lower than the height you want them to be. Once you have done this, prune the remaining stems creatively to create a natural layered look. It may also be necessary to thin out some of the interior branches.
- Watch Mark's video tips on pruning lilacs, azaleas, and forsythia.
The warm spring weather brings out the bugs:
Fungal diseases can overwinter in plant debris left in the garden. Be sure to rake old foliage and other plant debris out of your beds.
Be on the lookout for: