Decorating with natural materials has long been a tradition. The festive touches of fresh green plant stems, berries and dried natural materials add beauty and often fragrance to our homes.
Berries from holly, nandina and mistletoe are often associated with holiday decorating. There are several different similar looking plants found around the world that go by the name mistletoe. The mistletoe seen growing on tree limbs in our area is known as American mistletoe (Phoradendron leucocarpum). It is a common evergreen parasitic plant which grows on many native as well as landscape trees. Look for it in the south parasitizing oaks (water, willow and red), pecan, hickory, hackberry, Osage orange, river birch and green ash.
Mistletoe has green leaves containing chlorophyll and manufactures only part of its own food supply depending on the host tree for water and nutrients. Most trees that are otherwise healthy can tolerate a few mistletoe branch infections. Trees heavily infected over a period of several years often are reduced in vigor, become stunted and are more susceptible to harsh environmental conditions. Drought stress, harsh winter conditions, construction injury, diseases, insect infestations and other conditions can further weaken the tree resulting in death. Mistletoe is often a source of concern to homeowners with infected trees.
The male and female flowers of mistletoe are borne on compact spikes on separate plants in late fall and soon give rise to one-seeded, white berries. When ripe, they are filled with a sticky, semitransparent pulp, poisonous to humans, but safe to many fruit-eating birds. Mistletoe is spread by birds that feed on the sticky pulp. The birds discard the seeds which stick to their bills, feet and other body parts. Birds also excrete living seeds which are randomly deposited. The seeds are carried to other trees or other branches of the same tree and transferred from the bird and stick. Mistletoe seeds germinate in a short time. The parasite grows through the bark and root-like structures develop in the tree’s water-conducting tissue. These “roots” gradually extend up and down within the branch as the mistletoe grows. Mistletoe must be several years old before it is old enough to bloom and produce seeds.
Mistletoe is a slow-growing, but persistent plant. Its natural death is usually determined by the death of its host. The most effective method to control mistletoe is to prune out infected branches as soon as an infestation becomes apparent. Infected branches should be cut at least one foot below the point of mistletoe attachment to remove the embedded roots. Major branches that are infected cannot be pruned out. In these locations, mistletoe may be controlled by cutting it off flush with the limb or trunk and wrapping the area to exclude light. Several layers of wide, black polyethylene should be secured to the limb with cotton twine or flexible tape. This method takes several years to kill the mistletoe and may have to be repeated if the wrapping becomes detached.
Experts often encourage cutting all the mistletoe you can for decorative purposes, since removing the growth will benefit the host tree. But use caution if decorating with mistletoe as all parts of the plant are toxic. The stems and leaves are poisonous and can cause a skin irritation on contact. The small white berries from mistletoe are toxic and should be kept out of the reach of small children and curious pets.
While we use this traditional plant material for decorating during this festive season, it is often an unwelcome guest in many trees.