Mistletoe isn’t technically a weed, though it behaves like one in many situations. It’s a hemiparasite, a plant that attaches to trees and steals water and nutrients while also producing some of its own food through photosynthesis. Whether you call it a weed, a parasite, or a pest depends on context, but botanically, it occupies its own category that doesn’t fit neatly into the common definition of a weed.
Why Mistletoe Isn’t a Typical Weed
A weed, in the simplest horticultural sense, is a plant growing where it isn’t wanted. By that loose definition, mistletoe qualifies. But weeds are generally ground-level plants that compete with crops or garden plants for soil nutrients, water, and sunlight. Mistletoe doesn’t do any of that. It grows high in the canopy of host trees, never touches the ground after germination, and doesn’t compete with your garden plants.
Instead, mistletoe is a parasitic plant. It sends root-like structures called haustoria deep into a host tree’s branches, tapping directly into the tree’s vascular system to pull out water and dissolved minerals. Because mistletoe also has green leaves and photosynthesizes on its own, scientists classify it as a hemiparasite rather than a full parasite. It can make some of its own energy but depends on a host tree for water and nutrients.
How It Spreads From Tree to Tree
Mistletoe spreads almost entirely through birds. Its white or reddish berries are coated in a glue-like substance called viscin that makes seeds incredibly sticky. Birds eat the berries, then deposit the seeds on new branches through droppings, regurgitation, or by wiping their bills against bark to dislodge the clingy seeds. Some bird species are so specialized for eating mistletoe berries that they visit already-infected trees more frequently than healthy ones, which causes mistletoe to cluster heavily in certain trees.
Dwarf mistletoes, a separate group that primarily attacks conifers, take a different approach. They launch seeds explosively from their fruits, propelling them onto nearby branches. Seeds typically land on conifer needles first, then get washed down onto twigs by rain. From there, germination begins, and a visible swelling appears on the branch about two years later. Shoots emerge after another two years, and fruit production starts two years after that, making the full cycle roughly six years from seed to reproduction.
Is It Actually Harmful to Trees?
The Texas A&M Forest Service puts it plainly: mistletoe is generally not considered a serious pest, so you shouldn’t panic if you spot it in your tree. Light infections often go unnoticed, and many trees live with mistletoe for decades without significant decline.
Heavy infection is a different story. Mistletoe increases a tree’s water loss, and research shows this effect gets dramatically worse during heat waves, with water loss through infected branches rising up to fourfold on hot days. That extra water drain lowers the pressure in the tree’s internal plumbing, creating about an 11% increase in the risk of hydraulic failure, essentially the tree’s version of a circulatory collapse. During droughts, mistletoe is recognized as an important co-contributor to tree death globally. Individual branches can die even when the tree survives overall.
For the timber industry, the damage is substantial. Dwarf mistletoe alone causes several billion dollars in timber losses each year across western Canada and the United States.
Where Mistletoe Grows in the U.S.
North America has multiple native mistletoe species, all in the genus Phoradendron. The most widespread is Phoradendron serotinum, which infects over 100 tree species across the eastern United States. In the Southwest, Phoradendron californicum targets desert trees like mesquite and palo verde in Arizona, southern California, and southern Nevada. Texas and Oklahoma have their own species that favors hackberry and mesquite, while the Pacific Coast hosts species that primarily attack oaks, willows, and sycamores.
European mistletoe, the species most associated with holiday traditions, is not native to North America. It was introduced to Santa Rosa, California in 1900 by the horticulturist Luther Burbank and has remained confined to that area. California’s Department of Food and Agriculture gives it a high pest rating, and New Zealand has gone further, banning it outright as a prohibited plant. No U.S. state officially lists native mistletoe as a “noxious weed,” though, reinforcing the distinction between parasitic plants and weeds in regulatory language.
Its Ecological Value
Despite its parasitic nature, mistletoe plays an important ecological role. Researchers have tested what happens when mistletoe is experimentally removed from an area, and the result is measurable biodiversity loss. Sites where mistletoe was cleared lost a greater proportion of bird species that had been nesting in mistletoe clumps. The dense, bushy growth of mistletoe provides shelter and nesting habitat that many birds rely on, and its berries are a critical winter food source when little else is available. Some ecologists consider mistletoe a keystone resource, meaning its removal has outsized effects on the surrounding ecosystem.
How to Remove It From Your Trees
If mistletoe is light and your tree looks healthy, you may not need to do anything. But if you want to control it, pruning is the most effective approach. Cut infected branches at least one foot below the point where the mistletoe attaches. This matters because the haustoria, those root-like structures, extend well below the visible plant. Use thinning cuts that remove branches at their point of origin or back to a large lateral branch.
When mistletoe grows on a trunk or a major limb you can’t afford to remove, cut the plant flush with the bark and wrap the area tightly in several layers of wide black polyethylene to block light. This starves the remaining tissue. Even simply cutting mistletoe off each winter without wrapping is better than leaving it alone, since it reduces seed production and slows spread to other branches.
A plant growth regulator called ethephon can also knock back mistletoe when sprayed directly on its foliage. The best window is early spring before the host tree leafs out, on days when temperatures are above 65°F. Spray only the mistletoe itself, not the entire tree, and make sure the foliage is thoroughly wetted.