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Managing Mistletoe

Now that the oaks have shed their leaves, look for the green azalea-sized clusters of mistletoes (Phoradendron serotinum) nestled comfortably in the bare branches. This half-parasitic plant has been a part of our culture for centuries.

Mistletoe (Phoradendron serotinum) is a half-parasitic plant that has been a part of our culture for centuries.

Mistletoe (Phoradendron serotinum) is a half-parasitic plant that has been a part of our culture for centuries.
Bob Polomski, ©2018, Clemson Extension

The modern tradition of using mistletoe around the Christmas holiday season dates back to the Celts of northern Europe.  Druids, the holy men of Celtic society, used mistletoe in winter solstice ceremonies.  Fearing the cold, short days of winter, the Druids used this green symbol of growth to ensure the return of the sun’s warmth in the spring.

Other cultures associated mistletoe with fertility because of its ability to bear fruit in winter.  The Ainu of Japan chopped-up mistletoe leaves and scattered them on their fields to ensure a good crop.  In Austria, a sprig of mistletoe was placed in a couple’s bed to encourage conception.

These age-old rituals and traditions related to Druid beliefs and worldwide fertility rites likely inspired the modern tradition of kissing under the mistletoe on Christmas Eve. It began as a fad in England and Wales in the 18th century and has become a Christmas tradition in many households today.

In our trees, the mistletoe leaves allow it to produce some of its own “food,” but steals water and minerals from its host. In some cases, mistletoe is simply a cosmetic problem; in others, it can affect the growth and vigor of its host and expose the tree to attacks by diseases and insects.

In our trees, the mistletoe leaves allow it to produce some of its own “food,” but steals water and minerals from its host.

In our trees, the mistletoe leaves allow it to produce some of its own “food,” but steals water and minerals from its host.
Bob Polomski, ©2018, Clemson Extension

The only effective way of ridding your tree of a mistletoe infestation is by cutting the infected limb one to two feet below the plant because mistletoe “roots” may extend up to a foot on either side of the point of attachment.  Breaking off the tops only encourages regrowth. If you’re a do-it-yourselfer, avoid butchering the tree with haphazard cuts.  Employ the services of an ISA (International Society of Arboriculture)-certified arborist.

Mistletoe "roots" may extend up to a foot on either side of the point of attachment.

Mistletoe “roots” may extend up to a foot on either side of the point of attachment.
Bob Polomski, ©2018, Clemson Extension

Since the 1950s, scientists have been searching for cheaper and more effective methods of controlling mistletoe. No effective chemical controls are available at this time. Herbicides have been evaluated, but they may pose a threat to the host.  Growth hormone sprays, such as ethephon (Florel® Brand Fruit Eliminator), interrupt flowering or cause the shoots to fall off, but the mistletoe eventually resprouts and needs to be treated again.

Since trying to remove a heavy infestation can pose more harm to the tree than the mistletoe itself, it may make more sense to practice the modern, traditional use of mistletoe during this holiday season.

However, if you decorate your home with store-bought or home-grown mistletoe, hang it up high out of the reach of children and pets.  The berries are toxic and the sap may irritate the skin of some people.

Mistletoe berries are toxic and the sap may irritate the skin of some people.

Mistletoe berries are toxic and the sap may irritate the skin of some people.
Bob Polomski, ©2018, Clemson Extension

If this document didn’t answer your questions, please contact HGIC at hgic@clemson.edu or 1-888-656-9988.

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