You would expect to see a Hiroshima-type scene if you read headlines like “Nine Tornadoes Reported in Dallas-Fort Worth,” but that’s not always the case. Anyone who’s lived in north Central Texas knows about the damage that comes with spring storms and the tornadoes they spawn. However, even when tornadoes hit, as they did recently, damage to trees is hard to predict. Some general rules hold true even when the damage is randomly scattered throughout the property or even an individual tree. Three major components of limb or stem failure are branch aspect ratio, branch crotch angle, and “lion’s tailing.”
1.) Branch aspect ratio: The closer two connected limbs and/or stems get to being the same size, the greater the likelihood they will fail at the point of their union. If two limbs are mirror images of each other, they’re probably going to break apart.
2.) Branch crotch angle: Limbs/stems that have a narrow angle at their union (i.e. looks more like a “V”) tend to have included bark and poor attachments, resulting in greater risk of failure. Wider angles (i.e. unions shaped more like a “U”) are less likely to break, however, the branch aspect ratio rules still apply and can supersede branch crotch angles. In short, “U’s” are good and “V’s” are bad.
3.) “Lion’s tailing”: Limbs that have had their interior branches (those closest to the trunk) removed, leaving a tuft of foliage only at the end, are more likely to fail. The limb looks like a lion or poodle tail, hence the name. This creates a situation where the wind force impacts the limb only at the end furthest from its attachment to the tree. As anyone who covered physics in high school knows, leverage amplifies force making it easier to break the limb. From a health perspective, removing the inner canopy also starves the tree by eliminating its ability to make energy, especially during extreme summer heat.
