Why Do Eucalyptus Trees Fall Over?

Eucalyptus trees can be a particular pain for homeowners because of the chance that the trees will fall over. The eucalyptus tree can do some real damage to any structures -- or people -- it hits, despite its skinny, papery look. If your area is prone to high winds or flooding, or if the trees are very old, you must keep an eye on the trees and environmental conditions to help head off any pending disasters.

Roots not only provide a pathway for moisture and nutrients to reach the tree but also hold the tree in place in the soil. Roots can extend down as taproots or spread out around the tree. Eucalyptus trees are prone to falling because they have shallow spreading roots that don’t do a good job of steadying the tree in loose soil or when something places pressure against the trunk and branches.

Eucalyptus trees can be a particular hazard in windy conditions. If the winds are strong enough, they can easily topple the trees onto houses, cars and those unfortunate enough to be in the way. It’s not unusual to hear of downed trees after big storms or during Santa Ana wind conditions in places like Southern California. For example, the "San Diego Reader" reported that Santa Anas on Feb. 2, 2011, blew over three eucalyptus trees in Balboa Park in San Diego, and KPBS in San Diego noted the winds caused another tree to fall onto a freeway connector ramp. Santa Anas are strong, dry, warm winds that blow out of the desert into Southern California, raising the fire risk and creating gusty conditions.

Soil that becomes saturated from heavy rain or flooding isn’t as strong as dry soil when it comes to holding in tree roots. Large eucalyptus trees can fall over because the flooded soil isn’t strong enough to hold the roots of the top-heavy tree in place. Roots in older or diseased trees can also decay to the point where they can no longer keep the weight of the tree upright.

If you have eucalyptus trees in your yard or if they are close to your home or business, get them inspected if they’ve grown large enough to do damage if they fall over. If the trees are on city, county or state land, contact the appropriate government office; if they are in your neighbor’s yard, try to work something out with the neighbor, especially if an inspection reveals the tree is in danger of falling over. Laws governing the removal of eucalyptus trees vary from city to city. Some, like Lake Forest, California, require you to get a tree-cutting permit before undertaking any work on a eucalyptus tree, including pruning.