Dear Miss Floribunda,
My neighbor’s forsythia is blooming, and I recall some advice you gave a couple of years back. You said that when forsythia is blooming, it is time to prune rose bushes. Well, I don’t have any rose bushes, but I do have hydrangeas, azaleas and a mock orange. Is it time to prune them? Those hard frosts left brown leaves, so maybe I should take those off. I have never pruned any of these in the past, but perhaps I ought to and I’d like to know exactly when.
Biding My Time on Buchanan Street
Dear Biding My Time,
I confess that I play it safe and never prune my own hydrangeas or azaleas, or even my forsythia. They seem to do just fine without pruning.
However, it is true that hydrangeas can get leggy with time, and that some varieties produce larger blooms if pruned. The time you choose to prune depends on whether your plant is a variety that blooms on old wood or on new wood. Those that bloom on old wood should not be pruned till later in the summer, after blooming ends, and those that bloom on new wood may be pruned in spring.
Almost all azaleas bloom on old wood — but if you have a new hybrid variety, you should check to be sure — so pruning should be delayed for now.
Mock orange and forsythia bloom on old growth and, for the record, so do weigela, deutzia, lilacs, quince, viburnum and spirea. If you have any of these shrubs and think they need shaping, please stay your shears till after they finish blooming, and then do it within a month after they flower.
Plants that bud on new growth and should be pruned in early April include abelia, beautyberry, butterfly bush, roses, boxwood, holly and clethra.
If you have hedges of arborvitae or such conifers as cedar, fir, juniper, pine and spruce that perhaps are getting taller than you like, this is the time to clip them back. Never prune them in autumn; this causes them to put forth new growth that will be killed by frost, rather than encouraging the dormancy they need to survive winter, and the cuts you make will be susceptible to the fungi that are so prevalent in fall.
Hydrangeas are a little trickier than other shrubs because some varieties bloom on old wood, and some bloom on new wood. Mopheads (Hydrangea macrophylla), lacecaps (H. macrophylla, var. normalis), and climbing hydrangeas (H. anomala, subsp. petiolaris) bloom on old wood, and should not be pruned in spring. The reblooming kind, such as “Endless Summer,” will give you a second chance if you make a mistake, prune too soon and so prevent a first flowering. Varieties that bloom on new wood are oakleaf (H. quercifolia), such as “Snow Queen”; panicled (H. paniculata), such as “Limelight”; and smooth hydrangeas (H. arborescens), such as “Annabelle.” They should be pruned now before temperatures become too warm. The panicled hydrangeas grow very tall, up to 10 feet, so consider pruning to control and shape them.
Perhaps you are not sure what variety of hydrangea you have, much less whether or not they bloom on old or new wood. I sought advice from my neighbor, Hortensia Hedgeworthy, whose back garden is surrounded by them. She told me it is quite simple: Go outside and look at the stems of your plants. If you see buds beginning to form on their ends, leave them alone. They are old-growth hydrangeas and should not be pruned now. If you don’t see buds, or only a few new buds on new green sprouts rather than woody brown ones, then you have a new-wood hydrangea and can prune.
However, Hortensia cautions against severe pruning. She prunes her tallest down to perhaps three feet, never lower. She begins at the top, clipping just above the leaf node. This is the time when she removes the dried flower heads she had left intact over winter to give interest to the plant. Then, just as I advise for pruning rose bushes, she removes small side shoots from main branches to encourage larger blooms, and she cuts at a 45 degree angle to prevent water from settling on stems and encouraging rot.
She and I also agree that watering after pruning is very important. Even though pruning is good for a plant, it is not comparable to a mere haircut or a pedicure. It is in fact quite stressful for the recipient. Hydrating the shocked plant helps with healing and with establishing new growth. However, please don’t water so much as to cause root rot!
For common sense advice from experts in the Hyattsville Horticultural Society, please come to the next meeting on Saturday, April 18 at the home of Virginia Bennett, 4520 Madison Street, Riverdale Park. The 10 a.m. meeting will be followed by a plant exchange.
Miss Floribunda writes about gardening for the Life & Times. You may email her at Floribundav@gmail.com.