The Best Time to Trim Trees in Whatcom County

For most trees in Whatcom County, the best time to trim is the dormant season, and late winter before the buds break is the best part of it. The tree is resting, the structure is easy to see, and cuts close quickly once growth starts in spring.

There are exceptions. Some trees bleed sap, some are better pruned in summer, and some jobs cannot wait for any season. Clearing limbs off the roof before the November windstorms, for example, is about the house as much as the tree.

What is the best time to trim my tree?

It depends on the tree and on the reason for the work.

Most broadleaf trees: dormant season

Maples, birches, oaks and most ornamentals respond best to pruning between leaf drop and bud break. Cuts made then seal quickly once growth starts in spring.

Big conifers: most of the year

Douglas fir, western red cedar and hemlock are less sensitive to timing. Thinning, deadwooding and clearance can happen through much of the year, though we avoid the height of spring growth and the hottest, driest stretch of summer.

Fruit trees: late winter, plus summer

Apples and pears get their main prune in late winter with a light round in summer. Cherries and plums are often pruned after harvest in summer. Our apple pruning guide goes into the detail.

Hedges: late spring and late summer

Laurel, arborvitae and most hedges are trimmed once the spring flush has hardened off and again in late summer, so they go into winter tidy.

When to trim trees in Washington state?

West of the Cascades, the dormant season is the default, with one well known quirk. Maples, including our native big-leaf maple, bleed sap heavily if pruned in late winter as the sap begins to rise. It looks alarming, but it is harmless to the tree. If the dripping bothers you, prune maples in early winter or wait until the leaves are fully out in late spring or summer.

The time to avoid for heavy pruning on almost any tree is spring leaf-out. The tree has just spent its stored energy pushing out new leaves, the bark is loose and easily torn, and a big cut at that moment costs it the most.

What months should you not trim trees?

For heavy pruning, roughly April through early June is the window to avoid on most trees, while they leaf out. A few other cautions:

• Wet, mild autumn weather suits fungal spores, so on trees prone to canker it is better to wait until winter.
• The hottest, driest weeks of summer stress any tree, and large cuts add to it.
• Nesting season is when birds are most likely to be using the tree.

Light pruning, deadwood removal and anything that is a safety problem can happen any time.

What months can you not cut down trees?

There is no single month when tree work is banned across the board, but there are limits. Wild birds and active nests are protected under federal law, and state and local rules can add to that. In practice, spring through mid summer is when nests are most likely, so major removals and heavy pruning are best planned for autumn and winter. If we find an active nest, we stop and work out a plan before cutting.

Check with the city or county before any large removal, especially near water or on steep ground, where other rules may apply.

Get ahead of storm season

Our biggest windstorms tend to arrive from November onward, and the outflow winds that come down the Fraser Valley find every weak limb. The best time to deal with a dead branch over the bedroom or a heavy limb near the power drop is in October, before the first big blow, not the morning after.

A good pre-storm visit means removing deadwood, reducing long, heavy limbs over the house, thinning crowded growth lightly, and clearing branches back from the roof and the service line. It also takes moss and needle loads off the gutters.