Why Do the Mistletoe & Spruce Trees Live Together?

Eastern Dwarf Mistletoes are parasitic plants.

Mistletoes like the eastern dwarf mistletoe are parasites that thrive at the expense of their host. Eastern spruce dwarf mistletoe grows on spruce trees in the Northeast, slowly sapping their hosts and ultimately killing them.

Features

Mistletoes are flowering plants that colonize trees and obtain nutrients they need from their unfortunate hosts. They are hemiparasitic or semiparasitic, meaning that they are only partially dependent on their host; since they photosynthesize, they can derive some, though not all, of the energy they need from sunlight.

Function

Different species of mistletoe colonize different hosts; the eastern spruce dwarf mistletoe is the most common problem for spruce trees. While most seeds germinate in soil, the seeds of the mistletoe plant can germinate on a tree when carried there by birds. The mistletoe lives with the spruce so it can obtain sugar, water and amino acids it needs for growth; it does so by growing root-like projections that penetrate the stem of its hapless victim.

Potential

Over the course of 10 to 20 years, eastern dwarf mistletoe can slowly kill a spruce tree. As the tree devotes an ever-increasing amount of nutrients to the branches occupied by the mistletoe, its other branches die and fall off. Despite its romantic associations, mistletoe is far from beneficial for spruce trees.

References

• Bowdoin College: Summer Research: Why is Mistletoe a Kiss Goodbye for White Spruce?
• USDA: Eastern Spruce Dwarf Mistletoe
• Palomar College, Wayne's Word: Parasitic Flowering Plants