Mistletoe: Friend or Foe?

Mistletoe, the stuff of legend and tradition, grows in two varieties: dwarf mistletoe, found in the western United States, and leafy mistletoe, found in the southwest and Florida. While leafy mistletoe is not as deadly as its western counterpart, it can severely impact a tree’s health and vigor.

Mistletoe: the stuff of legend and tradition! As leaves fall in Florida and mistletoe becomes easier to see in trees, homeowners wonder about this biological squatter. Is it dangerous or is it not? Should it be eradicated or left alone?

Homeowners in managed communities can leave mistletoe decisions up to their landscape maintenance providers, but those responsible for their own trees should be informed so that they can make educated decisions.

Two Kinds of Mistletoe

There are two kinds of mistletoe: dwarf (Arceuthobium) and leafy (Phoradendron).

Dwarf mistletoe causes serious, deadly diseases in conifer trees of the western United States, Europe, Asia, and north Africa. In the U.S., lodgepole pines, Douglas firs, and western larches are tree species that have been most affected.

Dwarf mistletoe is leafless. It forms initially inside tree branches and depends on its tree host for water, nutrients, and support. The most obvious signs of infection are growth masses called witches’ brooms, which are large, dense clumps of branches, often distorted or deformed. When one or more witches’ brooms are in the crown of a tree, they hijack the tree’s nutrients, leading to a thinning of the crown and sometimes, ultimately, the death of the tree.

The U.S. Forestry Service says that control is accomplished by killing infected trees and thus preventing the spread of infection.

Leafy mistletoe is the mistletoe species found in Florida and the southwest United States. Like the dwarf, it is parasitic—it can only grow on a host plant, from which it draws nutrients and water.

Florida mistletoe has leaves and small flowers. It grows in round clumps attached to a tree branch by a single stem. These clumps can be five feet wide and weigh as much as 50 pounds.

Is Florida Mistletoe Dangerous?

Florida mistletoe is not as much of a threat to trees as the dwarf mistletoe found in the western United States. However, it bears paying attention to and taking active steps to get rid of it.

A mistletoe seed that is deposited (usually by a bird) onto a branch sends out a root-like growth into the bark of the tree. This grows into the inner tissues of the branch. From the seed then grow sprouts that become leaf-producing branches, forming the distinctive ball-shaped mass easily visible in trees—especially when tree leaves have fallen.

A tree that is heavily infested will have many clumps of mistletoe growing throughout its branches. These clumps all take water and nutrients from the tree, leaving it weakened and susceptible to pests and disease. A tree full of mistletoe can die, and the reason for its death can be disease or that it simply isn’t getting enough nutrients.

What to Do About Mistletoe

The University of Florida Extension Services recommend either manual or chemical controls of mistletoe.

Manual controls involve pruning out mistletoe clumps. This can be a challenge when clumps grow at the top of a tree. Renting a hydraulic lift is one way to accomplish mistletoe removal throughout a tree, even up high.

A growth-regulating chemical called Ethephon, applied in winter when a tree is dormant, is the other way to control mistletoe. This must be applied by a licensed pest control operator.

Once Florida mistletoe is in a tree, it can spread easily to nearby trees (usually by birds). Eradicating it from a tree will keep mistletoe spread on your property to a minimum.