Birches are among the first trees to leaf out in spring, so a birch that is still bare when the lilacs are blooming is worth a close look. Sometimes only the top of the tree is bare and the lower branches leafed out normally. Sometimes the whole tree is late, or leaves came out small and sparse. Each pattern points to a different cause.

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The short answer: if the top of a white birch is bare while the lower branches leafed out, bronze birch borer is the most likely cause. The larvae tunnel under the bark and cut off water to the upper branches (The Morton Arboretum). A whole tree that is late or sparse points to stress from the previous year, such as drought, winter injury, root damage or a recent transplant. Scratch a twig with your thumbnail: green underneath means it is alive, brown and dry means that part is dead.

Read the pattern

Pattern	Likely cause
Top of the tree bare, lower branches in leaf	Bronze birch borer
Whole tree late and sparse, small leaves	Drought stress last year, or root damage
Branch tips dead, buds dry and brown	Winter injury or dieback
New tree bare or with few leaves	Transplant shock
One large limb bare	Canker, borer or physical damage to that limb

1. Bronze birch borer

The Morton Arboretum describes bronze birch borer as a serious pest of ornamental birches, especially white-barked species. The first warning is yellowing and thinning of leaves in the upper crown, followed by dieback of the upper branches. The larvae tunnel under the bark, which cuts off the flow of water. Infestations often begin in branches about three-quarters of an inch to an inch thick and move down the tree over the years. A tree that was thin at the top last summer may simply fail to leaf out there this spring. Morton warns that the borer can kill the entire tree in two to three years if left uncontrolled.

Check for: raised, bumpy ridges in the bark of the upper trunk and branches, and D-shaped exit holes. The University of Minnesota Extension lists bronze birch borer first among the causes of dead branches in a birch canopy. Purdue University Extension notes that stressed trees are attacked most.

What to do: prune out dead branches back to live wood. Water deeply in dry spells and mulch the root zone. Ask a certified arborist or your extension office about treatment while most of the crown is still alive. If borers have killed much of the canopy, replacing the tree with a resistant birch, such as river birch, is often the better choice.

2. Drought the previous summer

Birch buds for this spring formed last summer. A hot, dry summer or fall can leave the tree with weak buds and little stored energy, so it leafs out late with small, sparse leaves. The Morton Arboretum notes that drought stress also makes trees more susceptible to insects and disease, which is why it often comes before borer attack. Water deeply this season, mulch, and expect recovery to take a year or two.

3. Winter injury

Cold snaps after a warm spell, drying winter winds and road salt can kill buds and twig tips. The tree leafs out from lower, protected buds while the tips stay bare. Scratch the bark of a bare twig. If it is green underneath, wait. Many birches push new buds a few weeks late. If it is brown and brittle, prune back to live wood after the tree has leafed out, so you can see what survived.

4. Root damage or a poor site

Construction, trenching, soil compaction, a change in grade or new paving over the roots can all show up as a sparse, late canopy a year or more later. Birches have shallow roots and are particularly sensitive. The Morton Arboretum notes that birches do best in cool, moist, partly shaded sites. A tree in an open, hot spot struggles each year.

5. Transplant shock

A birch planted in the last year or two may leaf out late or thinly while it regrows roots. The Morton Arboretum’s research found that a tree can lose up to 90% of its root system when dug from the nursery, and that recovery takes about a year per inch of trunk diameter. Keep it watered, about an inch a week on well-drained soil in summer and fall, and do not fertilize until it is growing well again.

Scratch test and next steps

Wait until a couple of weeks after your other birches or nearby trees have leafed out.
Scratch a few twigs on bare branches. Green means alive.
Look for D-shaped holes and bumpy bark on the upper trunk and limbs.
Prune dead wood back to living tissue in early summer.
Water in dry spells and mulch 2 to 4 inches deep.

If more than half the crown is dead, see how to tell if a birch tree is dying and our guide to birch tree diseases and pests.

Sources

Bronze Birch Borer, The Morton Arboretum
Bronze Birch Borer (E-50), Purdue University Extension Entomology
Birch: Dead Branches in Canopy, University of Minnesota Extension
Watering Trees and Shrubs, The Morton Arboretum
Caring for New Transplants, The Morton Arboretum

Top photo: Mathew5000, CC BY-SA 3.0, via Wikimedia Commons

Why Hasn’t My Birch Leafed Out? 5 Likely Causes