Spotted Coral-root Orchid

Corallorhiza maculata
Friday, July 11, 2014

            Without close inspection, this Organism of the Day is prone to be taken for a squawroot, or, worse, a dead and dried-up flower stalk. It resembles a squawroot, however, for precisely the same reason that squawroot resembles few other plants; both are parasites entirely reliant upon their host species for energy, without need for photosynthesizing green leaves. While not all orchids derive the entirety of their energy from mycorrhizal fungal relationships, all rely on such relationships to survive. Research published in 2012 found that the introduction of native orchid species to otherwise totally suitable forest habitat was futile if too little of the necessary species of fungi were present in the soil.

            C. maculata associates exclusively with mushrooms in the Russulaceae family. One study identified the species of fungus which it parasitizes by sampling fungal genetic material attached to the roots of the orchids themselves. Across 104 C. maculata individuals, 20 different species of russula were found in mycorrhizal associations with the orchid. However, there were no universal fungal partners; C. maculata growing under oaks had no fungi in common with orchids growing under conifers, and mycorrhizal community was not static between plants growing at low and high elevations. However, all spotted coral-root orchids rely on energy which their various fungal partners procure either from decomposing organic material or from symbiotic associations with nearby trees. It is unlikely that the fungi benefit at all from the interaction.

            C. maculata is a member of the genus of coral-root orchids, whose 11 members are mainly found in North and Central America. All coral-root orchids have underground, coral-like branching rhizomes, each branch of which may produce a flowering stem. However, each does not produce a stem every year; indeed, the entire plant may go unseen for years at a time. It continues to grow and carry on other life functions during these years, making it perhaps most accurate to regard Corallorhiza as a genus of subterranean plants that produce above-ground flowers.

            The English word “immaculate,” meaning totally lacking spots or blemishes, serves well to explain this orchid’s specific name, “maculata.” The small flowers that occur on the top third of the stem are unusual in shape. A central sepal extends from the top of the flower, flanked by a pair of petals slightly shorter than the sepals. Below these, two more sepals flare laterally to the right and left. The final petal (referred to as the lip) is broad and showy, with striking purple spots on a field of white. The five different variants of this species vary in characteristics such as the precise shape of the lip and the degree of spotting present. Two pollen sacs are located on the underside of a conspicuous, central style.

            C. maculata is thought to be pollinated by small bees, although the slight variation in flower shape between varieties suggests a variety of pollinators. They typically flower in mid-June to September, depending on the location and variety. This species is one of the most widespread in its genus, found throughout much of North America where conditions are right. It is partial to moist coniferous or subalpine forests rich in humus.

            This plant is growing behind Lewis.

Hazel Galloway