"Granddaddy" Health

By Gail Goldberger
The Morton Arboretum

Granddaddy needs geriatric care.

Just like older people, older trees have special health requirements.  We’re talking about so-called “granddaddies,” the majestic, older trees that define a neighborhood and always get noticed.

“Like many senior citizens, older trees shrink in height and their growth rate slows considerably,” says Edith Makra, arborist and Community Trees Advocate at The Morton Arboretum.  Their adaptability also reduces with age, so they’re less resilient against stresses such as disease, drought, pests, and disturbances. Install a sprinkler system, add a patio or driveway, and you might kill a granddaddy tree nearby.  The ill effects might not show up for several years, because granddaddies respond more slowly to change than younger trees. The depleted condition you see today may have been triggered by a change in the growing environment or conditions a few years prior.

A granddaddy’s weaknesses become more pronounced as the tree ages. For example, trees whose branches form a “V” at the trunk are at risk. As time goes on and the branches thicken, they begin to press against each other, creating stress and weaknesses. Such branches may break off. In the worst cases, the tree must be removed before it becomes a hazard to the area.

The Morton Arboretum recommends homeowners get their granddaddy trees inspected annually.

If your tree has V-shaped branching structures, look carefully to see if their union has split or cracked.  An arborist may be able to repair the problem either by strategically removing branches or shortening the limb to reduce the weight, protect the tree’s structure, and preserve as much of the crown as possible. Arborists could also apply a steel cable permanently to reduce the chance that a limb will tear off or fail. Or, they may insert long steel bolts through the base of the “V” and secure them with nuts, to support weak branches in danger of splitting off.

Old trees can often appear to be healthy, but fail structurally. The internal “skeleton,” the hardwood area, can decay and become unable to support major limbs or the trunk. A certified arborist needs to evaluate the overall structural integrity, which is done most easily in fall and winter.

Homeowners can watch for outward signs of decay, such as fungus or mushrooms growing from the trunk of the tree, or very near the base. Also, look for cavities in the tree, such as where squirrels or raccoons might live. Cavities may be too high to see from the ground, however, a telltale sign would be moisture along one area of the trunk, when the rest of the trunk is dry.  Another sign is a small tree growing out of your granddaddy tree in much the same way a tree or small plant can grow out of a gutter.

Mulch is especially important for granddaddy trees, because “the root systems need to be given every imaginable opportunity to keep growing and supporting the tree,” Makra says.  If a granddaddy is in trouble, cut, very short, any grass that’s within the “dripline,” – the ground between the trunk and the outermost tips of the branches. Then, apply up to an inch of compost, followed by 2-3 inches of double-ground wood-chip mulch. Do not apply chemical fertilizers, as these could be stressful to a granddaddy tree.

It’s important to water a granddaddy tree during the growing season into the fall. Water deeply but infrequently to keep the top 8-12 inches of soil moist.

Granddaddies are among the most valuable of trees. They provide the most shade, the most leaves to filter dirty air, add considerable worth to your property, and yield other benefits. Make sure you have a health care plan for granddaddies.

Gail Goldberger writes for The Morton Arboretum.