Is mistletoe harmful to your oak boughs?

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Last Updated: 
December 29, 2005

CORVALLIS - Look up into the bare branches of the oak and you will see dark clumps against the winter sky. That's mistletoe.

Famous in the myths of many cultures, mistletoe has long been a symbol of peace and friendship.

In Scandinavian antiquity, enemies that met beneath a tree filled with mistletoe would lay down their arms and declare a truce until the following daybreak. The Roman poet Virgil enabled his hero Aeneas to return safely from the underworld armed with a sprig of mistletoe. And ancient Celts hung mistletoe over their doors to bring happiness into the home.

But is this symbol of peace and friendship harmful to your oak trees?

It depends on the extent of the mistletoe infestation, according to Chal Landgren, a forester with the Oregon State University Extension Service.

A parasitic plant, mistletoe gets water and nutrients from its host plant, the oak tree. It is spread from tree to tree by birds that dine on mistletoe berries and spread the seeds through their droppings. Mistletoe seeds sprout, sending roots into the oak branches. If you snap off the mistletoe, it will grow back from roots within the oak branch.

A few clumps make little difference to a healthy tree, although 15 or 20 clumps can begin to sap nutrients. A professional tree care specialist can remove such large infestations of mistletoe.

There are many kinds of mistletoe, including dwarf mistletoes that parasitize conifer trees. Unlike the oak mistletoe, dwarf mistletoes can alter the growth pattern of trees, stimulating thick, broom-like sections to grow. Once considered undesirable, these dwarf mistletoe brooms have been found to provide nest sites for spotted owls and other forest creatures.

The mistletoes that grow on conifers are not as conspicuous as the oak mistletoe, with its fleshy leaves and sticky white berries. Let a sprig of oak mistletoe bring peace and happiness to your home this holiday. Sealed with a kiss.

Author: Peg Herring
Source: Chal Landgren