Garden Detective

Garden Detective: Birch tree is looking sad

I live in the Fair Oaks area and have noticed birch trees with dead branches at the top (including ours). Is there a disease in the area, and is the whole tree going to die?

– Lois Gulliksen, Fair Oaks

You are not alone. Birch trees are one of the most common landscape trees in our area. But they weren’t meant for drought – or long lives.

Your tree is probably a European white birch ( Betula pendula), according to the UC master gardeners. As these trees mature, the bark on the main trunk and limbs becomes white but is marked with deep, black clefts.

In the Sacramento region, the life span of a birch tree is approximately 25 to 40 years. Decline will often show in branch die-back or leaf drop. During drought, birch trees – which need consistent and deep irrigation – show signs of stress such as those dead branches. Or that die-back may just be signs of old age and a steady decline.

These trees often are compromised by where they grow – in the middle of a lawn. If irrigation was cut back during the drought, the tree’s water supply also was impacted. Also, anything that goes on the lawn goes into the tree.

The birch root system is extremely sensitive to fertilizers and herbicides, including weed-and-feed products as well as mechanical damage. Those will cause problems.

Lack of water and dry soil also will cause decline. The natural habitat of birch trees is the forest, where they grow alongside creeks and streams.

To determine the soil moisture, push a long screwdriver into the soil, working outward from the trunk to the drip line under the leaves. If the screwdriver does not easily penetrate the soil, then the tree must be irrigated.

Lay several lengths of soaker hoses, working outward from the trunk to the perimeter of the tree under the drip line. Attach a garden hose to the soaker hose and let the water drip for several hours until the screwdriver will easily slip into the soil.

If your tree is in a lawn, remove the grass from around the trunk out to the drip line and replace it with a layer of fine bark mulch, chopped red cedar bark or aged compost. A bender board around the perimeter of the mulch will prevent the mulch from working into the lawn.

With a little TLC, you may coax a few more years out of your birch.