Arcethobium pusillum (dwarf mistletoe)

by Molly Marquand, Herbert J. and Esther M. Atkinson Fellow

On April 16th, a day when most of Massachusetts celebrates the beginning of the revolutionary war, conservation staff members John Burns and Molly Marquand took a paddle on a nearby reservoir. Their sights were set on finding Arcethobium pusillum (dwarf mistletoe), a small and unassuming plant from a little known and largely parasitic family. 

The scourge of the spruce it feeds upon, dwarf mistletoe creates characteristic tangles of woody growth known as “witches brooms” on its host plant. Scanning Whitehall’s floating islands of spaghnum moss, sheep laurel, and highbush blueberry, John and Molly were able to identify the rare, otherwise inconspicuous mistletoe by seeking out these dense twig masses in the crowns of affected black spruce. Confirming their find required navigating up shallow channels and clambering on board the inundated islands. A glimpse under the lens revealed not only that this was exactly the plant they had been looking for, but also, the plant was in flower!

A dioecious species, dwarf mistletoe plants are either male or female. Sporting 3 or 4 petal-like sepals and sessile stamens loaded with pollen, John and Molly’s first specimen was a male. Female flowers are less to look at, but produce a tiny berry that matures later in summer. Forcefully ejecting itself when ripe, dwarf mistletoe berries are covered in a sticky substance, which helps them adhere to nearby branches, or seed vectors, like birds.  Unlike other seeds, germinating dwarf mistletoe grows down, away from light and towards the pull of gravity. Piercing the cortex of its host tree, the young dwarf mistletoe begins its slow and steady path to establishment.

It can take several years for shoots to reemerge, and several more before the mistletoe is ready to bloom, which makes John and Molly’s find even more special! What better way to celebrate Patriots’ Day than to spend time up close with some real Americans- the native plants that have inhabited this landscape for thousands of years?