If they've done nothing else, mistletoe plants have mastered the art of survival. Most of us know mistletoe only an excuse to steal holiday kisses, but more than 1,300 mistletoe species live by larceny. Numerous evolutionary advantages let the tenacious evergreen shrubs steal food from trees, often to the point of starvation. This parasite-tree bond is a "'til-death-do-us-part" proposition, and mistletoe survives as long as its host remains alive to feed it. Growth-regulating spray slow mistletoe's spread, but only complete removal eradicates an infestation.
Mistletoe Survival Mechanisms
European and American mistletoe (Viscum album, Phoradendron leucarpum), commonly harvested for the holidays, are perennial in U.S. Department of Agriculture plant hardiness zones 6b through 8 and 6 through 11, respectively. Like all mistletoe, they tempt hungry birds with sticky-seeded winter berries. The birds deposit the seeds onto trees in their droppings or scrape them from their beaks onto branches. The clawlike roots, or haustoria, the germinating plants sink into the branches and trunks drain food, water and minerals. At up to 5 feet around and 50 pounds, mature mistletoe may weaken of break its branch. Nutrient, water and branch loss eventually combine to kill mistletoe-infested trees.
Things to Consider
On trees in your yard, mistletoe is a bad thing. But in the forest, it shelters squirrels and birds, including mourning doves, chickadees and wrens. Three species of hairstreak butterflies feed only on mistletoe leaves as caterpillars, and drink its nectar as adults. Although allegedly toxic to people, mistletoe's berries provide winter sustenance for deer, elk and porcupines. Birds and small animals nest in the cavities of mistletoe-killed trees. Before removing it, consider the consequences for wildlife.
Removing Young Mistletoe
Mistletoe needs two to three years to begin producing seeds, notes Texas A&M Forest Service. Pruning the visible parts of the immature plants before they set seed helps contain an infestation. Use clean, sharp pruning tools disinfected in rubbing alcohol between cuts and after you finish. Seal the pruned material in plastic bags for disposal.
Removing Mature Mistletoe
To remove mature mistletoe, cut small branches back to lateral ones or to the point where they emerge from the trunk. Removing all the haustoria requires cutting at least 1 foot below the mistletoe-covered sections. This technique isn't an option for major limbs or infested trunks. On those, prune the visible mistletoe back to the bark and wrap the affected areas with heavy, black polyethylene sheeting. Secure the sheeting with tape; retape or replace it as needed. The light-deprived mistletoe eventually dies, but it may take two years.
Safe Removal Practices
Whether pruning mistletoe plants or entire branches from a tree, put your own safety first. Never prune branches near power lines. If the job requires a ladder, secure it to the tree. Have someone with you to help in case of an emergency. Cut the branches in sections, and make sure the area is clear when they fall. Seriously infested trees may need complete removal.
- National Wildlife Federation: 12 Things to Know About Mistletoe
- Purdue University Consumer Horticulture: Mistletoe (Phoradendron Leucarpum)
- ZipcodeZoo.com: Viscum Album
- ZipcodeZoo.com: Phoradendron Leucarpum
- Wayne's World: Parasitic Flowering Plants
- Texas A&M Forest Service: Mistletoe
- UC Statewide IPM Online: Mistletoe
- UC Statewide IPM Online: Quick Tips: Mistletoe