Swing safely in your summer hammock

A lazy hammock swaying between trees sounds lovely, but it’s important to hang it in a way that is safe for both you and the tree.

“Never tie a rope or strap around a tree,” said Sharon Yiesla, plant knowledge specialist in the Plant Clinic at The Morton Arboretum in Lisle. “That is likely to damage the bark and underlying tissue. It can harm the tree or even kill it.”

To hang a hammock safely, clip it to screw eyes sunk into the wood. “You will only have to make a small hole and the tree’s bark will seal around it,” she said. “The tree will be fine.”

Buy large, sturdy, stainless steel or galvanized steel screw eyes at least 6 inches long. Use an electric drill with an appropriately sized bit to drill holes. Then twist the screw eyes into the holes.

Tying ropes or straps around a tree’s trunk or branches causes harm because it can damage important tissue just beneath the bark. That is the tissue that conducts water between the tree’s roots and its leaves. “If you damage those vessels, you’ve cut off the water flow,” Yiesla said. “The tree can’t survive if it can’t move water.”

That kind of damage — when water-moving tissue is cut through all around the trunk or branch — is called “girdling.” It can be lethal.

Trees can be damaged or killed near campgrounds when campers leave rope from hammocks tied around tree trunks. As the tree grows wider, the forgotten rope girdles the tree.

Trees also can be damaged or girdled by a slack line play set — a set of swings, ladders and other play equipment suspended from a rope that is often tied between two trees. A swing hung from a tree branch is a hazard too: As children play and the ropes, chains or straps move back and forth, they can gradually rub right through the bark. Decay or disease can enter the wound.

“Hanging a swing from a tree branch is risky to begin with,” Yiesla said. “But if the branch is girdled and dries out, the wood will become brittle and more likely to break.”

Trees can be girdled in many ways, such as by rope or wire left behind when signs are tied around them or by forgotten holiday lights. Even a ribbon made of non-biodegradable plastic tied around a tree trunk can girdle a tree if it is not promptly removed.

“To be safe, just don’t ever tie anything around a tree,” Yiesla said.

Instead, hang your hammock from sturdy hooks and rest easy.

For tree and plant advice, contact the Plant Clinic at The Morton Arboretum (630-719-2424, mortonarb.org/plant-clinic, or plantclinic@mortonarb.org). Beth Botts is a staff writer at the Arboretum.