Issue: October 27, 2007

Yes, mistletoe grows in New Mexico

I live a little north of Socorro and I noticed dark green leaves in some cottonwood trees. When I looked more closely, it looked like the mistletoe that I buy every winter for decorations for parties. Is this really mistletoe? Does it grow here?

Jane J.

Answer:

The broadleaf mistletoe that people use for holiday decorations does indeed grow here. That is probably what you saw in the cottonwood trees.

Mistletoe is a parasite, so it is not good for the trees. Several types of mistletoe parasitize trees in New Mexico. The one you described infests broadleaf trees. It is most common in southern New Mexico, but has been moving up the Rio Grande valley to the north. It is in your area. This particular mistletoe is a semi-parasite. It is green and able to photosynthesize to make its own food, but it depends on the host tree for water and minerals. It causes the tree to divert much of the needed water and minerals to the side of the tree with the mistletoe at the expense of growth and health in other parts of the tree.

If you want to use it for decoration, remember that mistletoe is poisonous. Using live (not artificial) mistletoe can be somewhat hazardous if you have children who may put the leaves, stems, or fruits into their mouths. You can help limit the spread of this undesirable plant by picking it from the tree and using it for decoration. Picking it from the trees is good even if you do not use it for decorative purposes. To limit its spread, pick all of it and allow none of it to form berries. It is by means of the berries that it will spread as birds eat the fruit and wipe the sticky seeds off on the branches or trunk of uninfested trees.

There are chemicals that can help in this process. One such chemical is ethephon that causes the growths to die back to their point of attachment on the host tree. Unfortunately, the mistletoe's roots (called haustoria) remain alive in the wood of the host plant after picking or chemical removal. New mistletoe grows back from the remaining haustoria. If you choose to use this chemical follow the label directions carefully and apply it only when the trees are dormant.

If you want to remove the mistletoe completely, you can prune away the branches containing the mistletoe. You will need to remove all the haustoria when you remove this branch. That means you will need to cut at least a foot below the signs of mistletoe on the branch. There is usually a swelling of this branch below the mistletoe indicating the growth of the haustoria inside the branch. Cut well below the swelling to be sure no haustoria remain. If the mistletoe grows from the trunk of the tree, removal may require total removal of the tree.

Marisa Y. Thompson, PhD, is the Extension Horticulture Specialist, in the Department of Extension Plant Sciences at the New Mexico State University Los Lunas Agricultural Science Center, email: desertblooms@nmsu.edu, office: 505-865-7340, ext. 113.

For more gardening information, visit the NMSU Extension Horticulture page at Desert Blooms and the NMSU Horticulture Publications page.

Send gardening questions to Southwest Yard and Garden - Attn: Dr. Marisa Thompson at desertblooms@nmsu.edu, or at the Desert Blooms Facebook.

Please copy your County Extension Agent and indicate your county of residence when you submit your question!