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Posted by Erica Glasener | Dec 14, 2011

Resisting Mistletoe

We're not talking about resisting what goes on underneath it. Horticulturist Erica Glasener discusses the fact that this iconic plant is actually a parasite.

Mistletoe growing in an Oak tree. Photo by Erica Glasener.It may come as a surprise to some people that mistletoe (Phoradendron species)  used for festive holiday decorations — the attractive white berries and evergreen foliage — is a parasite (meaning it takes advantage of other plants called hosts for its survival)  and,  is native to many parts of  North America. 

In my own yard, mistletoe resides in the tops of several large oak trees where it looks like large evergreen pompoms. Depending on where you live in the US, it is also found growing on a number of other trees, both conifers and deciduous types including juniper, cypress, apple, birch, alder, maple and cottonwood.  All of these host trees provide the necessary nutrients and water for parasites, in this case, the various species of mistletoe. 

Birds feed on the berries, then they excrete the living seeds which germinate and put down root-like structures into the branches. If you are concerned about mistletoe infesting your trees there are a few things to consider.

Assess the Infestation

In my oak trees the mistletoe does not seem to show any ill effects. The trees are old and established and are growing happily. If, however, your trees are declining, stunted in growth and generally not healthy, here are some methods of control to consider for mistletoe infestations.

Pruning:  Only in severe cases should you remove an infested tree; it is often a source of seed for mistletoe that can infect trees located nearby. When possible, remove young infected branches as soon as you notice infestations. If you are uncertain about the best way to prune your tree consult with a professional arborist. Branches should be removed where they originate or back to a large lateral branch. Remove shoots of mistletoe before they set seeds. This will reduce new infestations that occur when seeds germinate and start the cycle over again. This will not be a permanent solution but will reduce infestations. 

Plant trees that are resistant to mistletoe in your region:  Check with your Cooperative Extension Service for a list of trees. Research indicates that there are strains of mistletoe that are locally adapted and in one region they may prefer one type of tree over another. Choose resistant species when planting new trees. 

Chemical control: Chemicals to control or eradicate mistletoe should be used only with extreme caution. There are plant growth regulators such as etherphon (the trade name is Florel) that can be effective for controlling mistletoe. These only work if used when the tree is dormant and mistletoe is completely wet to the point where the spray drips off the foliage. Using chemical controls when trees are actively growing can result in damage or death to your trees. 

Is mistletoe poisonous? 

Yes, if you eat the mistletoe native to North America. Contact poison control for more information.

Should this ruin your holiday?

No. We're not being the Grinch; we just like to relate seasonal topics to actual home & garden issues. For obvious reasons, we don't recommend planting your holiday mistletoe plants.

Erica Glasener is a Networx - http://www.networx.com - writer. Get home & garden ideas like this - http://www.networx.com/article/resisting-mistletoe - on Networx.

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