Does Desert Mistletoe Kill Trees? (You May Be Surprised)

Desert mistletoe is a natural part of the desert ecosystem. Is it a parasite that kills trees? Or is it less harmful than purported? The truth may surprise you.

Most Americans are familiar with the custom of kissing under the mistletoe at Christmas. But when you’re in the desert southwest, mistletoe has a different reputation and kissing is definitely not involved.

Desert mistletoe, (Phoradendron californicum) is a different species from the bouquets of Christmas mistletoe (Phoradendron tomentosum). It’s a leafless plant with dense clusters of jointed stems that grows on trees. In the winter it produces inconspicuous but fragrant flowers which are followed by attractive red berries.

Its native range includes parts of the Mojave and Sonoran Deserts. And it has a reputation as a tree-killer. But is this deserved, or is this plant getting unfairly blamed?

Does Desert Mistletoe Kill Trees?

When I first learned of mistletoe, I was told that it is a parasite that sucks the nutrients out of trees and kills them. Frankly, it sounded pretty scary and like something you’d want to eradicate by any means possible before it kills your trees.

But let’s take a closer look at desert mistletoe, the part it plays in the desert ecosystem, and why waging war on it is not necessary (and invariably futile).

Desert Mistletoe is a Not a True Parasite

Desert mistletoe is not a true parasite, it’s a hemiparasite (hemi meaning half). This means it can photosynthesize and create most of its own food. But what it does need most from its host plant is water.

Like all mistletoe, the desert species doesn’t have roots — it has root-like structures called haustoria that penetrate the host plant to get water and nutrients. Hausteria’s name derives from the Latin word haustor, meaning “drinker of water.”

Desert mistletoe is spread by birds who eat the berries and then poop on a branch where the seeds sprout.

While mistletoe roots (I mean haustoria) are developing, it can take two years before mistletoe is visible! So by the time a clump of desert mistletoe is big enough for you to notice, the haustoria have been growing deeper into the plant. (This is why pruning will never be a cure.)

Desert mistletoe grows almost exclusively on trees, most commonly on mesquites, palo verdes, ironwood, and acacias. But it can occur on desert buckthorn or creosote shrubs.

As trees lose their leaves in the fall, you may be surprised to “suddenly” see a clump of desert mistletoe in one of your trees. (It’s not that it’s new, it’s just that they grow slowly and are hidden by leaves until they reach a noticeable size.)

These plants and desert mistletoe have evolved to co-exist over their thousands of years of existence. It’s been pointed out that it wouldn’t be in desert mistletoe’s best interest to kill its host which would also bring about its own demise.

Fun fact!
There are over 1500 species of mistletoe.
They can be found on every continent (except Antarctica).

How to Manage Mistletoe

You can’t prevent desert mistletoe, and you can’t cure it. You can only manage it, if that’s what you choose to do.

The most effective means of managing desert mistletoe is removing an infected branch as soon as it’s discovered. An infected branch should be pruned to a main lateral branch that is at least one foot below the infection. But be aware this is a temporary fix and it will grow back.

However, it’s thought that periodic removal helps to alleviate some of the stress placed on the host plant.

In an otherwise healthy tree, desert mistletoe will only weaken it slightly. Remember, that these plants have evolved to exist together.

I’ve heard that you can help your tree by giving it more water to replace the water the mistletoe uses. It’s doubtful whether this helps, since desert mistletoe wouldn’t use any more water than any other plant growing within a tree’s root zone.

And the root systems of desert trees cover a lot of territory, extending 4 times beyond the tree’s canopy, so most trees have numerous plants that potentially “steal” its water.

Benefits to Wildlife

Desert mistletoe doesn’t just take, it also contributes to the desert ecosystem.

Desert mistletoe berries are the primary food of the phainopepla (Phainopepla nitens), a bird whose name appropriately means “shining coat.” These striking birds have a noticeable crest, like a cardinal. The males are shiny jet black while the females are gray-brown. They are only found in the desert southwest.

Mockingbirds and gila woodpeckers also partake of mistletoe berries. And I’ve seen birds, especially Gambel’s quail, spend the night in a protective cluster of desert mistletoe. Coming full circle, desert mistletoe can help their host trees by attracting insect-eating birds.

Desert mistletoe is also a larval host for numerous butterfly species, including the iridescent blue great purple hairstreak.

Is Desert Mistletoe the Same As Witches’ Broom?

Desert mistletoe and witches’ broom are often confused with one another. They may look alike, but are not the same thing.

Desert mistletoe is one specific plant that occurs only in the desert southwest.

Witch’s broom, on the other hand, is not one disease or organism, and it occurs all over the world.

The term “witch’s broom” is an umbrella phrase used to describe a condition where a plant’s own cells grow abnormally. It can have a wide variety of underlying causes, usually bacterial, fungal, or viral infections. But it can also be caused by herbicide damage or genetic mutations.

Witch’s broom is known to occur on dozens of desert landscape plants. It also affects many economically important plants including blueberries, strawberries, fruit & nut trees, alfalfa, potatoes, chocolate, and wheat.

Recommended Reading
Are The Weird Growths on Your Plants Witch’s Broom?

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Photo Credits

Stan Shebs, CC BY-SA 3.0, Wikimedia Commons

Lip Kee Yap, CC BY-SA 2.0, Wikimedia Commons

University of Maryland Extension