Above Image: Howard, R.A. Provided by Smithsonian Institution, Richard A. Howard Photograph Collection. United States, Louisiana, Orleans Parish, New Orleans; USDA-NRCS PLANTS Database.
Many folks think of mistletoe as the plastic greenery you can buy to hang up at holiday parties that couples use as an excuse for smooching underneath. This mistletoe folklore apparently has its origins in Norse mythology, but we’ll skip that discussion today. There is an actual mistletoe plant, and it’s a parasitic plant!
There are many species of mistletoe in the United States. American or true mistletoes, Phoradendron spp., and specifically, oak mistletoe, appear to be the most common mistletoes in Indiana, according to U.S. Department of Agriculture Plants Database. Lindsey Purcell, former urban forestry specialist at Purdue, said the genus name, Phoradendron, translates to “tree thief,” referencing its hemiparasitic nature.
“Mistletoe contains chlorophyll,” said Purcell. “It can generate some energy, but the majority of its needs are taken from the host tree.”
Purcell said that mistletoe pierces trees with a root-like structure, called a haustorium, that absorbs nutrients and water. It creates additional photosynthetic areas for the tree, but it typically takes more than it gives. In large amounts, mistletoe can even stunt its host’s growth or kill it.
“Most mistletoe in Indiana is artificial, and for good reasons, since it is inaccessible and dangerous,” said Purcell. “Our region is prohibitive to growth except for extreme southern Indiana. It is too cold here.”
“Mistletoe is highly toxic to pets and humans,” warned Purcell. “Especially the berries, which have the highest concentration of phytochemicals.” Mistletoe has small, leathery leaves and translucent, white berries.
Janna Beckerman, Professor of Botany and Plant Pathology at Purdue University, wrote about another mistletoe, dwarf mistletoe. She said while true mistletoes mostly parasitize broadleaf trees and shrubs, dwarf mistletoes parasitize conifers.
Dwarf mistletoe is more common in the western United States.
“There are male and female plants, and the female plants produce the fruit,” she said. “These fruits are the bomb, in that each seed is explosively discharged like a water-propelled rocket – going up to 60 miles an hour!”
She said that seeds can be dispersed up to 50 feet, although distances in the 30 ft. range are more common. “The seed is coated with a sticky goop called viscin, which allow it to stick to any needles it strikes,” she said. “When it germinates, it produces a root-like sinker to penetrate the branch and begin its parasitic lifestyle.”
So, whether you buy into the folklore of mistletoe or not, its parasitic growth habit does not seem to exude love for others.
Access Purcell’s original article at https://ag.purdue.edu/stories/unexpected-plants-and-animals-of-indiana-american-mistletoe/, and Beckerman’s original article at https://ag.purdue.edu/department/btny/ppdl/potw-dept-folder/2021/th-oter-mistletoe.html.