The Bay Gardener

By Dr. Frank Gouin

Now’s the Time to Prune Sprouty Trees

Lilac, apple and maple are too busy growing to produce suckers

Some trees and shrubs produce heavy water sprouts or suckers when pruned in the spring. These include apple, crabapple, cherry, maple, hawthorn, pear, persimmon, oak, lilacs and viburnum. By delaying pruning of these species, especially severe pruning, until late June and July, you will be significantly reducing the number and growth of water sprouts or suckers arising from the area where the branches were pruned and from the roots.

By spring, roots have stored a large reserve of nutrients and sugars. When spring arrives, these move up into the stems and branches. If 25 percent or more of the branches have been pruned away, it means that all of the energy is directed to the remaining growth and vegetative buds. The result is excessive growth in some areas of the plant.

During the months of June and July, the plant is starting to replenish its roots for the next year. By pruning in mid summer, when there is less reserve energy, the plant maintains normal growth.

Thus if you have a crabapple or other tree that has outgrown its space, now is the time to prune it severely without fear of causing it to produce excessive growth of suckers or water sprouts that you will have to prune away again next year. When making heavy cuts, do not coat the cut surface with paint or tree-wound dressing. Research clearly demonstrates that coating cut surfaces actually inhibits healing of wounds.

Encouraging Iris

Q Everybody’s irises are lovely but mine. I’ve never done well with them, but the bulbs I planted in a rocky sun spot perhaps eight years ago have given me stalks full of flowers until this year, when I only got one blooming stem.

With your help, perhaps I’ll enjoy my own irises next year.

A I suspect you are refering to bearded iris. Most likely the rhizomes, called pachymorphs, have become overcrowded, and the time has come to dig them up and space them out again. Also inspect each pachymorph to make certain that the iris borer has not invaded them. Discard those that have become infested. Amend the soil with about two inches of LeafGro, and replant the pachymorphs, spacing them about four to six inches apart.

However, this project should be delayed until August.

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The Bay Gardener

By Dr. Frank Gouin

Now’s the Time to Prune Sprouty Trees

Encouraging Iris

Ask Dr. Gouin your questions at [email protected]. All questions will appear in Bay Weekly. Please include your name and address.