The Dogwood, belonging to the Cornus genus, is an ornamental tree prized for its distinctive flowers, attractive foliage, and sometimes colorful winter stems. Gardeners frequently seek guidance on how and when to prune this plant to maintain its characteristic shape and ensure abundant blooms. The timing of these cuts is a frequent source of confusion, particularly concerning the active summer growing season. This article addresses summer pruning for dogwoods, detailing the associated risks and outlining the optimal timing and techniques for maintaining a healthy specimen.
Why Summer Pruning is Generally Not Recommended
Pruning a dogwood during the height of summer, when temperatures are consistently high, subjects the tree to increased stress that can compromise its health. The primary risk involves the tree’s response to heat and water loss, as transpiration—the process of releasing moisture through leaves—is accelerated in warm conditions. Making significant cuts forces the tree to redirect energy toward wound closure (compartmentalization) instead of maintaining essential functions under heat stress.
Open wounds created by pruning also become direct entry points for numerous pests and diseases that thrive in the summer climate. The dogwood borer (Synanthedon scitula), a clearwing moth whose larvae target wounded trees, is active from May through October and will lay eggs on fresh cuts. Common fungal issues like powdery mildew and various leaf spots are more prevalent in warm, humid summer conditions, finding an easier foothold on a tree already weakened by pruning trauma.
Summer pruning can also disrupt the tree’s natural growth cycle, especially for flowering varieties. These trees set the buds for the following spring’s blossoms in the previous summer, meaning major cuts can inadvertently remove next year’s potential flowers. Therefore, summer pruning should be strictly limited to removing dead, diseased, or damaged wood—the “3 Ds”—which is a necessary sanitation measure. This emergency pruning should never extend to major structural shaping or size reduction.
Identifying the Optimal Time for Major Pruning
The most favorable window for major structural pruning of dogwoods occurs during the late winter or very early spring when the tree is fully dormant. Dormancy is the ideal time because the lack of leaves allows the gardener a clear view of the tree’s structure to make informed decisions about shape and branch removal. This timing minimizes the physiological shock to the tree, as its metabolic activity is low, allowing it to conserve energy for wound sealing once the growing season begins.
Some dogwoods, particularly the species Cornus florida, may exhibit “bleeding,” or the weeping of sap, if pruned too late in winter or early spring as the sap begins to rise. While this sap flow is generally not harmful, it can be messy and may attract certain pests. Pruning before the buds begin to swell entirely avoids this issue.
For flowering varieties, a secondary, less intensive pruning window exists immediately after the spring bloom has faded. Pruning at this time allows for the removal of spent flowers and minor shaping. This gives the tree the entire remaining growing season to recover and set new flower buds for the subsequent year. This post-flowering trim is preferable to the risks associated with pruning later in mid-summer.
Essential Dogwood Pruning Techniques
Regardless of the season, all pruning cuts must prioritize the tree’s natural defense mechanisms to ensure proper healing. Proper technique requires making cuts just outside the branch collar, which is the slightly swollen area where a branch meets the trunk or a larger limb. Cutting into the collar impedes the natural healing process, as this area contains specialized cells that form a protective barrier against decay.
It is important to avoid leaving stubs, which cannot heal and become entry points for pests and decay. For branches thicker than about one inch, employ a three-cut method to prevent the bark from tearing down the trunk under the branch’s weight. This method involves an undercut, a top cut to remove the weight, and a final clean cut at the branch collar.
A common task is the removal of suckers (shoots from the base or roots) and water sprouts (shoots higher up on branches). These vigorous, vertical shoots drain energy from the tree and should be removed cleanly back to their point of origin to maintain structure.
Pruning also involves distinguishing between two types of cuts:
Thinning Cuts
These remove an entire branch back to the source to increase air circulation.
Heading Cuts
These shorten a branch and should be used sparingly, as they can encourage weak, bushy regrowth.