Mistletoe (Viscaceae Family)

Main sources: Dimmit, Mark, "Viscaceae (Loranthaceae), in Phillips, Steven & Patricia Comus, eds., 2000, A Natural History of the Sonoran Desert, p. 260,Tucson: Arizona-Sonora Desert Museum Press; Epple, Ann, 1995, A Field Guide to the Plants of Arizona, p.80, Helena, Montana: Fountain Press;

Mistletoe is classified as a "partial parasite", because it generates its own chlorophyll photosynthesis, but it also draws both water and nutrients from its host tree or shrub, in some cases eventually killing the host plant. In our Saguaro Juniper area, two species are prominent -- "Desert Mistletoe" and "Juniper Mistletoe".

Desert Mistletoe (Phoradendron californicum et al.)

Desert Mistletoe (of which we find six species in Arizona) occurs from southern Nevada into Baja California and Sonora, and invades mainly our Sonoran Desert-typifying leguminous trees and shrubs. In the banner photo above, the host is a mesquite tree, the mistletoe displaying a sharply contrasting reddish color to the mesquite's green leaves; in the two photos below, an acacia shrub is the host. Leaves are nearly absent in Desert Mistletoe, which forms inconspicuous yellowish green flowers in the wintertime, with male and female flowers on different trees. The whole plant forms a "dense cluster of brittle, jointed stems" (Dimmitt, p. 260), as illustrated below, in this photograph from January 2005:

The female flowers produce small, pinkish berries, illustrated in the closeup of the above plant, shown below:

These berries are much favored by Phainopepla and some other local birds, who play important symbiotic roles in spreading the plant.

Juniper Mistletoe (Phoradendron juniperinum)

This mistletoe occurs mostly on Junipers (and typically, is located at higher elevations than the Desert Mistletoe). We photographed this old juniper tree in October of 1999 in Upper Cottonwood Seep Wash, when it was much infested by mistletoe (all of the clustered growths possessing a more yellowish green tinge than the rather grayish leaves of the tree itself in the photo below), and we actually experimented on this occasion by removing those invaders we could climb to reach. (For a better view of our work with this tree, click on Juniper.)

In January 2005 we returned, to find the tree looking much healthier, but some of the parasitic plants we had torn out had regenerated, and others (as the large & high-situated one at left below) had been missed.

Click on each image to enlarge it.


As you can clearly see from the enlargements, the leaves are yellowish-green, and the right-hand photo shows both a young growth (regenerating after our cropping efforts of 5 years earlier) and two of the whitish berries that characterize this species. Birds also feed on these berries. See also Juniper trees for a further account of this tree and its history.