Mistletoe in Trees

Robert J. Souvestre  |  12/21/2011 3:26:21 AM

Mistletoe clumps attached to branches in a water oak tree.

As a kid riding his bicycle in Metairie looking up in trees, I wondered how I could gather the mistletoe growing in the tree tops to sell for Christmas money to buy gifts. A pipe dream maybe -- but for a kid growing up with a twig of this traditional branch hanging in the living room meant a kiss from every female who entered our house.

Mistletoe was common in area trees but it was not a common commodity in retail stores. So I thought collecting and selling it may prove to be a promising entrepreneurial venture. I was wrong. Not that it may have been a good seller, but that it grew higher in trees than what I wanted to risk life and limb.

As leaves fall and expose bare tree branches, this chlorophyllous parasite may become more prominently in view. Mistletoe is a plant-parasitic seed plant that attaches itself to host trees like oak, pecan, ash, elm, sweet gum, hackberry, hickory, tulip tree and sycamore.

Birds are attracted to the berry shape seed and readily feed on this food. The seed pulp is sticky so birds wipe their beaks onto tree branches to remove the sticky seed. In doing so, they spread mistletoe from branch to branch and tree to tree.

Does mistletoe kill trees? This parasite can stress trees, especially in times of drought, and can kill branches they are growing on if the tree is in a weakened state of health brought on by environmental conditions or construction activity. The plant uses water and nutrients from the tree for its own growth but returns nothing to the tree. Even when the tree is under stress, the plant will continue to take water and nutrients from the tree branch it is growing upon.

Once the mistletoe seed germinates, a root-like haustoria develops enabling it to tap into the tree’s vascular system. This is the tissue that conducts water and nutrients within the tree. It is this haustoria that enables mistletoe that is cut from the branch to regrow.
 
Even on healthy trees mistletoe can be bad because it adds additional weight and mass to the tree branch. Branches containing mistletoe can become weaker in strength, which increases the potential for structural failure from wind or weight.

There is no practical control for mistletoe. You can cut the plant from branches. This provides short term relief but the plant regrows from the portion that remains attached and growing from within the tree branch.

You can remove the portion of the branch it is growing on but birds will continue to spread seed and after a few years you will have pruned your to tree to a stub.

Various chemical applications have been investigated to kill plants or retard mistletoe growth but none offer long term control. And the cost of applying these chemicals needs to be considered. The best advice is to maintain tree health by watering in the absence of adequate rainfall.
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