In the Garden:
Louise Clarke of the Morris Arboretum of the University of Pennsylvania removes water sprouts as part of her winter pruning schedule.
Winter Blades in Motion
From her window in the Morris Arboretum Horticulture Center, Louise Clarke had been eying for weeks one thick water sprout in an otherwise young, nicely shaped magnolia 'Miss Honeybee.' The mottled, ash-colored scaffold branches of a cucumber magnolia grow horizontally with tips reaching toward the sun. In spring, 'Miss Honeybee' proffers fragrant, tulip-shaped, creamy yellow flowers. This cucumber magnolia (Magnolia acuminata var. subcordata) blooms young and is a compact 20 to 30 feet tall at maturity.
Scaffold branches form a tree's framework. Water sprouts resemble cowlicks in an otherwise sleek hair cut. To a tree lover, they can be as annoying as fingernails scratching a chalkboard. Water sprouts are errant, fast-growing, vertical shoots taking a right angle from a healthy branch. They're mostly considered a no-no because they divert considerable energy from the tree's overall growth.
The 'Miss Honeybee' in the arboretum's Bloomfield Farm woodlands is newly planted and healthy. Clarke intends to keep it that way. On a sunny January afternoon, she grabs her gloves, pruning saw, and loppers. Getting a stable foothold in the snow, she examines the 2-inch thick water sprout and determines that the small, sharp, foldable saw is the most effective tool.
She angles the saw blade and cuts just outside the branch bark collar -- the swelling that looks like a doughnut where branch joins trunk. That bulge is a protective collar pushing from the trunk to surround the branch's base. It's considered a branch protection zone because protective chemicals generate there to inhibit nasty organisms and prevent branch decay. Left to nature's own devices, the tree will provide sufficient hormones to heal the wound and cordon off the area so the trunk and other branches remain unaffected and healthy.
Dealing with Water Sprouts
Water sprouts tend to return. Experts recommend removing young, thin sprouts by hand with a quick tearing motion. Some say this technique inhibits sprout regrowth. If your tree has many water sprouts that return after removal, something is wrong. The tree may be responding to stress such as root loss, root damage, storm damage, branch loss, topping, disease, over-pruning, improper thinning, drought, and more. Consult an arborist to correct the cultural problem before the tree is too damaged to survive.
As Bloomfield Farm's section leader, Clarke is responsible for acres of meadows, woodlands, and informal tree and shrub plantings. In late winter (January and February), she does "formative" pruning of young trees and shrubs.
Pruning annually to shape a young tree and shrub through its first four or five years of growth makes for a well-formed, healthy woody plant at maturity. Formative pruning usually involves thinning to remove excess, old, or crossing branches at the trunk or at the soil line.
Thinning opens the plant to more light, better air circulation, and water penetration. Thinning is not done from an upright, clip-off-the-branch-tips position. Correctly thinning shrubs involves squatting or sitting, reaching deep into the shrub to saw or prune off dead, old, thick, and crowded branches within 4 to 6 inches of the ground.
Invest in a topnotch pruning book with clear photos, explanations, and instructions. In this unsettled world, you may just enjoy the Zen and satisfaction of learning to prune correctly.
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