Arceuthobium spp., or dwarf mistletoes, are leafless, yellowish-green to olive-green, parasitic plants that infect coniferous, evergreen trees in our forests. As parasitic plants, dwarf mistletoes need to attach to a host plant to extract nutrients and water for survival. They do this through the production of root-like structures that grow into the living tissue of their host tree. Dwarf mistletoe can have significantly harmful effects on their hosts – causing reduced seed development, increased susceptibility to insect or pathogen attack, a reduction in tree growth, and even premature death.
Dwarf mistletoes are notoriously difficult to determine to species. Their flowers are tiny and inconspicuous. The fruits have the best diagnostic characteristics, but are dispersed in August and September. Interestingly, these fruits also make dwarf mistletoes one of the “fastest” plants on the planet – they produce sticky seeds that are explosively discharged from the fruit at nearly 60 miles per hour! The best way to determine which dwarf mistletoe you encounter in winter is to determine the identity of the host plant. Although each species can infest other hosts, they typically have a “favorite.” For instance, Arceuthobium americanum is primarily found on lodgepole pine, A. cyanocarpum on limber pine, A. douglasii on Douglas-fir, and A. vaginatum on ponderosa pine.
See if you can locate dwarf mistletoe on evergreen trees in the surrounding forests. Photograph the entire tree as well as a close-up of the dwarf mistletoe for each observation. This will help Denver Botanic Gardens document its range as well as monitor overall tree health. Post your findings to iNaturalist so they will be automatically added to the December EcoQuest iNaturalist project as well as the overall Denver EcoFlora Project
WHAT IS AN ECOQUEST?
EcoQuests, part of the Denver EcoFlora project, challenge citizens to become citizen scientists and observe, study, and conserve the native plants of the City via iNaturalist, an easy-to-use mobile app.
HOW DO I GET STARTED?
WHAT IS THE GOAL?
The EcoFlora project is designed to meaningfully connect citizens with biodiversity, and to assemble novel observations and data on the metro area’s flora to better inform policy decisions and conservation strategies.
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