How to Create and Maintain Snags and Cavities in Living Trees


Trees can support an incredible variety of life.

There are a number of ways you can create snags or dying parts of living trees. First, survey your property to see which existing snags you can leave. Then, consider creating new ones. A healthy, sustainable forest may have between five and ten percent of its standing trees as snags and living trees with cavities. Some forestry experts recommend three, six, or up to a few dozen snags per acre. It depends upon region, habitat, tree species, tree size, and the wildlife a landowner hopes to attract.

Check state or local wildlife agencies or forestry departments for recommendations for your area, and to discuss the best snag-making techniques and the best local tree species that provide long-lasting snags.

 Choose the trees you kill or wound carefully, picking ones with many defects, for example, or ones that compete for sunlight with trees you want to keep alive. If you regularly thin your forest, this is a good time to mark or create snags. Eventually, snags will fall and become logs (also valued by wildlife), so you will want to recruit other trees as snags age. You don’t want snags near your home or by well-used trails or anywhere else a falling tree might do harm.

A few considerations when creating snags:

● Snags may be grouped or scattered through a forest.

● Designate and create new snags as other ones age.

● Larger snags accommodate the largest range of species. Fifteen inches diameter at breast height or longer is usually optimal. In many cases, it takes a tree 80 years or more to reach this size.

● Deciduous species often make longer-lasting snags or den trees, though conifers also make fine snags. Birch and aspen don’t live long or last long as snags but they can provide homes for small species. Species good for long-lasting snags include: white and black oaks, cottonwood, elm, beech, and big-leaf and sugar maples.


There are several ways to create snags or provide cavities in still-living trees. These include:

Girdle a Tree

Chop a four-inch-wide ring through the outer and inner bark in a complete circle around the trunk. Trees weaken around the girdling point, so cut this ring as high on the trunk as possible. You can also just girdle large branches to provide part of the tree as a snag.

The Tall Stump

Cut a tree high up, leaving a six to seven foot tall stump. (Higher if safely possible.)

Remove a tree’s top and a half of its large branches

● “Plant” Snags

Haul a snag to a preferred site and put it in a hole as deep as at least one third the snag’s length, or set it in a base of concrete or secure it to a very sturdy post. (Be careful not to introduce snags from pest-infested areas.)

Cavities in Living Trees

Many living trees have dead portions. You can create these as well. Here are a few techniques:

● Well above head level, cut a heavy branch (five or more inches thick) approximately six inches from the trunk.

● Drill one-inch or wider holes, facing downward, into the trunk.

● Chop off a large square of bark to create an open wound in a trunk.

In time, these wounds should form cavities.

It may take a few years for the tree to die, or for a cavity to form.

For more information on snags, see:

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