- Author: Help Desk Team
Note: This was originally published in the Contra Costa Times.
Q: I have a lot of mistletoe in my street tree, which is some sort of ash, I think. Is it a problem and if so, how do I get rid of it?
A: Broadleaf mistletoe is an evergreen parasitic plant that grows on a number of landscape trees in California and can be readily observed on deciduous trees once the leaves have fallen. Modesto ash is especially susceptible to mistletoe infestations. As a parasite it absorbs both water and mineral nutrients from its host trees. Healthy trees can tolerate a few branch infections, but individual branches may be weakened or sometimes killed. Heavily infested trees may be reduced in vigor, stunted, or even killed, especially if they are stressed by other problems such as drought or disease.
The Mistletoe Lifecycle:
Mistletoe is either female (produce berries) or male (produce only pollen). The berries of the female are small, sticky, and whitish. Birds feed on and digest the pulp of the berries and excrete the living seeds which stick to any tree branch on which they land. After the seed germinates, it grows through the bark and into the tree's water- conducting tissues where rootlike structures called haustoria develop. These haustoria gradually extend up and down within the branch as the mistletoe grows, and for that reason if you simply remove the visible portion of the mistletoe, it will often resprout.
Controlling Mistletoe:
The most effective way to control mistletoe and prevent its spread is to prune out infested tree branches. Remove branches at their point of origin on the main trunk or back to a large lateral branch and cut at least one foot below the point of mistletoe attachment. Mistletoe infecting the trunk or a main branch where it cannot be pruned may be controlled by cutting off the mistletoe flush with the limb or trunk. You must then wrap the area with a few layers of black polyethylene to exclude light. Use twine or tape to secure the plastic to the limb, but do not wrap it too tightly or the branch may be damaged. Broadleaf mistletoe requires light and will die within a couple of years without it. It may be necessary to repeat this treatment.
Harvesting for the Holidays:
Simply cutting the mistletoe out of an infested tree each winter, even without wrapping, is better than doing nothing at all. Even though the parasite will grow back, spread is reduced because broadleaf mistletoe must be several years old before it can bloom and produce seed. Time your pruning right and you will have plenty of mistletoe for the holidays.
For More Information:
For more information on mistletoe and its management, the University of California has a free publication located at: https://ipm.ucanr.edu/PMG/PESTNOTES/pn7437.html
Help Desk of the UC Master Gardeners of Contra Costa County (EDC)


- Author: Shannon Wolfe
One of my favorite parts about the Christmas season is getting to bring a tree into my living room. I love the smell of an evergreen tree, and having one right next to my couch can't really be beat. I am certainly not alone in my love for greenery, and for bringing some of the outside inside. In fact, ancient cultures also used greenery to symbolize good luck and ward off evil-spirits during these darkest days of the year. I enjoy learning about the winter time traditions of other cultures and how they fit into how we celebrate Christmas today. A lot of these pre-Christmas traditions focused on a whole Christmas season, and on protecting the home from evil spirits that lurked during these darkest days of the year.
The Romans decorated with greenery for the New Year and also gave each other gifts known as strenae, sprigs and green branches gathered from the sacred groves of the woodland goddess of strength and endurance, Strenia. These evergreens were symbols of good luck for the year ahead. Sweet honeyed dates, figs, or small pieces of jewelry sometimes accompanied the strenae. Children were given small gifts, such as clay figurines or bags of nuts that could also be used as game tokens. To this day, gifts during the Christmas season are known as strenna in Italy and New Year's gifts are etrenne in France.
In preparation for the Twelve Days of Christmas (the twelve days following Christmas, December 26-January 6), prickly holly was placed around windows and doors - like evergreen barbed wire - to keep the roaming evil spirits, witches, goblins and trolls from entering the home and to protect the good fairies. Every sprig of evergreen had to be removed by the Twelfth Day or else bad luck would fall upon the home. The admonition to take down evergreens at the end of the Twelve Days was also applied to Christmas trees after they were incorporated into Christmas customs.
Advice From the Help Desk of the Master Gardeners of Contra Costa County
MGCC Help Desk Response: I'm responding to your request to the MGCC Help Desk and provide some information about how you might try to eliminate or at least manage and reduce further spread of the mistletoe that has invaded your Japanese Maple.
As you know, mistletoe is a parasitic plant that lives on trees. Mistletoe is the common name given to several parasitic plants that grow on trees. It absorbs both water and nutrients from the tree. While an otherwise healthy tree can tolerate a couple of mistletoe infestations, trees that are stressed become even more stressed from the presence of mistletoe. Also, about 3 or 4 years after mistletoe starts growing on a tree, if the plant is a female, it can start producing sticky seeds which can fall and infect other branches or can be carried by birds to new locations. For these reasons, the University of California recommends that the problem be managed (http://www.ipm.ucdavis.edu/PMG/PESTNOTES/pn7437.html).
If it is possible to remove the branches or a portion of the branches where mistletoe is attached, that approach is the most likely to rid the tree of the infestation. If you use this approach, you will want to make your pruning cuts at least a foot below the location where the mistletoe is attached. The reason to make the cuts well below the attachment point is because the mistletoe creates rootlike structures in the water conducting tissue of the tree. These structures extend both up and down the branch. Removing the branch at least a foot below the point of attachment makes it more likely that you will remove the rootlike structures. If you fail to remove them, the mistletoe can regrow from the root structures. Before undertaking your pruning, you might also want to look at this University of California website which has a diagram depicting how the root like structures develop in the tree's tissue above and below the point of attachment of the mistletoe.http://www.ipm.ucdavis.edu/PMG/WEEDS/ID/mistletoechar.html
Also, as mistletoe can easily spread from tree to tree, you might want to encourage any neighbors with infected trees to take steps to eliminate infestations in their trees.
Finally, if you see that the tree is being stressed from the drought, giving the tree some additional water should help reduce the tree's stress. In addition to a deep watering approach, if you don't already have mulch around the base of the tree, you might want to add some. The mulch layer can help the soils retain water. Mulch 3-4 inches deep under the canopy of the tree. Avoid placing mulch immediately next to the trunk as it could harbor insect pests and diseases that may harm the tree.
We hope that this information is useful in your efforts to help your tree become and remain healthy. You're welcome to contact us again, either at a Farmers Market or through our Help Desk, if you have further questions.
Help Desk of the Master Gardeners of Contra Costa County
Note: The Master Gardeners of Contra Costa's Help Desk is available year-round to answer your gardening questions. Except for a few holidays, we're open every week, Monday through Thursday for walk-ins from 9:00 am to Noon at 75 Santa Barbara Road, 2d Floor, Pleasant Hill, CA 94523. We can also be reached via telephone: (925) 646-6586, email: ccmg@ucanr.edu, or on the web at http://ccmg.ucanr.edu/Ask_Us/
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