Pinedrops is the common name for the plant Pterospora andromedea of the family Ericaceae; it is the only species in the genus Pterospora. It grows in coniferous or mixed forests in heavy soil. It is native to North America from southern Canada to the mountains of Mexico and is most commonly found in the western half of the continent, though small populations are found in the northeast United States and eastern Canada.
The visible portion of Pterospora andromedea is an unbranched flower spike (raceme) generally 30-100 cm in height, though it has been reported to occasionally attain a height of 2 meters. The above-ground stalks are usually found in small clusters between June and August. The stalks are hairy and feel somewhat sticky to the touch. They have scale-like structures that are described by some authorities as vestigial leaves or sterile bracts. The upper portion of the red stalk has a series of yellowish, bell-shaped flowers that face downward.
Pterospora andromedea is a particularly interesting plant due to its lack of visible chlorophyll (trace amounts were identified by Cummings and Welschemeyer in 1998, but not enough to provide energy for the plant or to color it). They exist for most of their lifecycle as a mass of brittle, but fleshy, roots. The mass is rarely greater than 7 cm in diameter, and between 10-40 cm under the soil surface. They live in relationship with mycorrhizal fungi that is not yet well understood, described as either parasitic or symbiotic upon the fungus by different experts. Whatever the exact relationship, they derive all their carbon from their associated fungus, which entirely covers the outside surface of the roots. They are thus usually described as mycorrhizal heterotrophs or myco-heterotrophs.
They live in association with a very limited number of fungi including Rhizopogon subcaerulescens, R. arctostaphyli, and R. salebrosus. A note of caution: unlike plants, fungi are not yet well categorized and so species' names are likely to change frequently as more research is done and the genus Rhizopogon is particularly hard to taxonomically categorize. Pterospora has yet to be discovered with any species outside the genus Rhizopogon.