The Bay Gardener

by Dr. Frank Gouin

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Pruning Is like a Good Haircut for Hardwood Shrubs

But take care with conifers

A reader wanted to know what she should do about the azaleas in front of her house that were so large she could not see out the window. My advice: Prune them back to at least two feet below the window ledge.

She responded in shock: “Are you crazy or something? That will kill my babies.”

For most plants, pruning is like getting a haircut. You can severely prune hardwood species such as azaleas, hollies, rhododendrons, viburnums, forsythia and butterfly bush. They will generate new branches and resume normal growth.

Hardwood species produce an abundance of vegetative buds at the axis of nearly all their leaves. As the plants grow, these buds are constantly being pushed outward but remain dormant; thus they are known as latent buds. Hardwood species also have the capability of producing adventitious buds, which are similar in behavior to adventitious roots produced when you root cuttings.

Severe pruning doesn’t work for coniferous plants such as arborvitae, cedar, fir, juniper, pine and spruce. Coniferous species are not capable of regenerating stems after being pruned severely because they bury their dormant buds with bark and don’t produce adventitious buds. However, they are capable of producing adventitious roots, and many of these species are propagated from cuttings.

Thus if you have overgrown hardwood shrubs, don’t be afraid of pruning them back severely. If the plants flower in early spring, cut them back as soon as they finish flowering. The earlier you prune them back, the sooner the new growth will emerge. Broadleaf evergreens such as hollies, cherry laurel and boxwoods should be pruned back before new growth appears.

Do not fertilize or irrigate except in drought. The plant you are pruning has an extensive root system that is fully stocked to force the plant into spring growth. Do not interfere with that root system by fertilizing or with excessive applications of water.

More Lawn Advice

Q When is the best time to aerate? I see that the golf courses aerate spring or fall. If it is advisable to do either time, I would prefer the fall because I have dogs and the spring rains produce more mud and dirt for them to track into the house.

I have tall predominately tall fescue grass, but there is a blade of grass growing that has a white wheat-looking top to it. It started growing in last year after applying some tall fescue top seed. When the grass is cut three and a half to four inches tall, the white tops are not as noticeable. When longer, this grass takes away from the uniformity I was looking for.

–Catherine Davidson, Annapolis

A If you are going to aerate your lawn, do it in September using a core aerator. Then spread compost at the rate of two cubic yards per 1,000 square feet if you are going to do any good.

Cut your grass to a height no less than three and a half and preferably four inches. I am currently cutting my lawn at five inches now that I have a new mower, and it is looking even better than ever. The grass you top-seeded with was most likely the old K-31 tall fescue. Fescues develop a seed head that is similar to wheat.