Maples have a reputation for being fussy about pruning, mostly because of the sap. Cut a maple in late winter and the wound can drip for days. That leads many people to wonder whether summer is a better time. The short answer is yes, for light trimming. Summer is a good time to remove dead wood, clear low branches and tidy the crown. What you should avoid in summer is heavy pruning that takes off a big share of the leaves.

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The short answer: you can trim a maple in summer. Light pruning, such as removing dead, broken, crossing or low branches, can be done at any time of year with little effect on the tree, and pruning a maple after its leaves are fully out avoids the heavy sap flow of late winter and early spring. Avoid heavy pruning of live wood just after the spring flush of growth, and avoid removing a large share of the canopy in hot, dry weather. Major structural pruning is best done while the tree is dormant.

Why maples “bleed”

Maples move a lot of sap in late winter and early spring, before the leaves open. Iowa State University notes that maples, birches and elms “bleed” heavily when pruned at that time, but that the loss of sap does not harm the tree, and the flow eventually slows and stops. The Morton Arboretum still advises avoiding spring pruning of maples because they are bleeders and lose a large amount of sap. It is mostly a cosmetic issue, but many people prefer to avoid the mess and the dark staining on the bark.

Once the leaves are fully expanded, sap pressure drops and cuts barely drip. That is one reason summer pruning appeals for maples.

What the ISA says about timing

The International Society of Arboriculture gives three useful rules:

Most light, routine pruning to remove weak, dead or diseased limbs can be done at any time of year with little effect on the tree.
As a rule, growth and wound closure are maximized if pruning takes place before the spring growth flush, which means late winter.
Heavy pruning of live tissue just after the spring growth flush should be avoided, especially on weak trees.

Putting those together for maples: do structural pruning in the dormant season if you can tolerate some bleeding, do light trimming in summer, and avoid heavy cuts in late spring and early summer when the tree has just spent its energy pushing out new leaves.

Good jobs for summer

Dead and broken branches. They are easy to see when the rest of the tree is in leaf. Remove them any time.
Diseased twigs. Cutting out wilting branches is part of managing verticillium wilt. Penn State Extension advises pruning out affected limbs and watering to maintain vigor.
Clearance pruning. Raising low limbs over a path, patio or driveway.
Small corrective cuts. Removing a crossing or rubbing branch, or a small competing leader on a young tree.
Japanese maples. Light shaping of Japanese maples is often done in summer, when you can see the form clearly with the leaves on.

What to avoid in summer

Heavy thinning or large cuts. Leaves make the tree’s food. Removing a large share of them in summer leaves the tree with less energy, which is why the ISA cautions against heavy pruning of live tissue after the spring flush.
Pruning during drought. A drought-stressed maple has little to spare. Water deeply first and wait for cooler weather. The Morton Arboretum notes drought stress can make trees more susceptible to some diseases and insects.
Topping. The ISA calls topping perhaps the most harmful pruning practice known. Never cut a maple back to stubs to reduce its size.
Big jobs in late summer and fall. Save major cuts for the dormant season, when the ISA notes growth and wound closure are maximized after pruning.

How to make a good cut

Cut just outside the branch collar, the slightly swollen area where a branch joins the trunk. Do not cut flush with the trunk, and do not leave a stub.
For branches thicker than about an inch, use the three-cut method: an undercut a foot or so out, a top cut just beyond it to drop the limb, then a final cut at the collar. This prevents the bark from tearing.
Use clean, sharp tools. Disinfect between trees if you are removing diseased wood.
Do not paint or seal the wound; let the tree close it naturally.

When to call an arborist

Hire a certified arborist for anything you cannot reach from the ground, for limbs over a house or wires, and for large structural cuts. The ISA Find an Arborist directory lists certified professionals.

Summer pruning at a glance

Task	Summer?
Remove dead or broken branches	Yes
Cut out wilting or diseased branches	Yes
Raise low limbs for clearance	Yes, light
Remove a large share of the canopy	No, wait for dormancy
Structural pruning of a young tree	Best in late winter
Topping	Never

For month-by-month timing, see the best month to trim a maple tree. If your maple has dead branches you cannot explain, read why my maple tree is dying.

Sources

Pruning Your Trees, International Society of Arboriculture, TreesAreGood.org
Sap Is Flowing from a Pruning Cut on My Maple Tree, Iowa State University Extension
Japanese Maple, The Morton Arboretum
Maple Diseases, Penn State Extension
Plants to Prune in March, University of Minnesota Extension
Watering Trees and Shrubs, The Morton Arboretum

Top photo: Hartsough1990, CC BY-SA 4.0, via Wikimedia Commons

Can You Trim a Maple Tree in the Summer?