Does Mistletoe Harm Trees?
Mistletoe is a common plant throughout North Carolina that can be found growing on the branches of deciduous trees. This same mistletoe is often harvested and brought indoors during the holidays, where it is hung in doorways to provide an excuse for stealing a kiss. Though often considered a pest, there are several things that should be considered before deciding if this plant is a friend or foe.
While mistletoe can grow on more than 100 different types of trees, it is most often found on pecan, hickory, oaks, red maple and black gum in North Carolina. Mistletoe is a small evergreen shrub that is semi-parasitic on other plants. Instead of producing roots in the ground, mistletoe sends out root like structures into tree branches, from which it steals water and nutrients. The tree the mistletoe grows upon is known as its host. As a green plant, mistletoe does contain chlorophyll and is able to make some of its own food, so it does not completely deplete its host tree.
Mistletoe is most easily seen in winter. Look for ball shaped green masses up to 3’ wide connected to otherwise bare tree branches. Each mass in a tree is an individual mistletoe plant and a single tree may host only a few or many mistletoe plants. Birds are responsible for spreading mistletoe by seed. They relish its white berries, which ripen in early winter. When birds feed on these berries, the seed inside the berry passes through the bird’s digestive track surrounded by a sticky film that helps the seed stick to tree branches when it comes out the other end. Areas where trees are heavily infested with mistletoe are often indicative of a healthy bird population.
Is Mistletoe Harmful?
Mistletoe spreads and grows relatively slowly and is rarely considered an immediate threat to tree health. Healthy trees are able to tolerate a few mistletoe plants with little harmful effect. Trees that are heavily infested with mistletoe may become less vigorous, stunted, and can possibly be killed if subjected to additional stress from drought, extreme temperatures, root damage, insect infestation, or disease.
Like many organisms that at first appear to only be pests, mistletoe also has some benefits. It is tremendously valuable to wildlife, particularly birds and insects. For most property owners, the presence of mistletoe should be considered a sign of a diverse ecosystem rather than a threat to tree health.
If mistletoe is growing on trees in your yard the best thing you can do for them is to provide extra water during drought and an annual spring application of slow release or organic fertilizer. In addition, apply a 2”-3” layer of mulch or ground leaves around trees from the trunk out to the edge of the canopy. This will reduce competition from grass, conserve moisture, and protect trees from injury by mowing equipment.
If there are trees on your property where mistletoe growth cannot be tolerated, you can control it by pruning out the infested branches. Simply cutting the mistletoe back flush with the branch will not kill this parasite, though it will help slow its growth and spread. In a tree where many branches would have to be removed to rid it of mistletoe, simply letting nature to take its course is the better option as removing multiple branches is harmful and often fatal to trees.
Pruning trees to remove mistletoe is best done in winter by a certified arborist. Certified arborists are highly qualified tree professionals who have passed the certified arborist exam offered through the International Society of Arboriculture. A list of certified arborists practicing in North Carolina can be found on their website, www.isa-arbor.com.
Use with Care
If you are considering harvesting mistletoe to bring indoors during the holiday, be sure to place it carefully. The white berries of our native mistletoe are poisonous and may cause stomach and intestinal irritation with diarrhea, lowered blood pressure, and slow pulse if ingested. While an average adult would have to eat several berries before becoming sick, pets and children may be more sensitive. Make sure to keep mistletoe well out of their reach.
Learn more about mistletoe’s lore, natural history, and management in landscape trees from these online resources:
- This site from Florida Extension includes tips on controlling mistletoe and using it for decoration: http://solutionsforyourlife.ufl.edu/hot_topics/lawn_and_garden/mistletoe.shtml
- Lots of interesting facts about mistletoe are included in this post from the Hilton Pond Center for Piedmont Natural History, located in SC: http://www.hiltonpond.org/thisweek051208.html
- See more images of mistletoe here: http://www.carolinanature.com/trees/phle.html
Use Extension Search to find research based information from Cooperative Extension systems across the U.S.
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