Spirals appear frequently in nature. In plants, one easily recognizable spiral pattern is in the arrangement of seeds on a sunflower head. Many plants also have leaves arranged in a spiraling pattern around the branches to catch the maximum amount of sunlight. A spiral arrangement of flowers on the stem, however, is rather unusual, and the list of potential candidates is short.
Named for the Greek word for spiral, plants of the Spiranthes genus are members of the terrestrial orchid family, colloquially known as ladies' tresses. Most ladies' tresses are characterized by a flower stem which appears to be twisted, hence the name's reference to hair; white flowers grow in a conspicuous spiral pattern upward along the stem.
More than 30 species of Spiranthes are found throughout the world, with many occurring in North and Central America. Plants re-seed easily, but are scarcely found in established plant communities, preferring instead to colonize pastureland or recently disturbed sites. The Spiranthes species occur in all 50 states; within some geographic regions, plants within the species may be easily confused with one another, as they are so similar in appearance.
Details of the plant's flowers offer further identifying marks. Flowers are usually white, tubular and up to half an inch long, featuring a characteristic orchid-like structure with two small upper petals and a large lower petal, or lip. The interior of the lip ranges in color from green to yellow or orange; spent flowers fade to brown and wither on the flower stalk. Many Spiranthes varieties have fragrant flowers, though the plant's short stature means that you have to be fairly close to the ground to appreciate the fragrance.
Other Identifying Characteristics
The flower stalk of most Spiranthes species usually emerges from a basal rosette of leaves, or a cluster of leaves arranged in a circular pattern around a central point. Leaves can grow to be 10 inches in length or more. In some species, the upper surface of the leaf is covered in fine, bristly hairs. The flower stalk is the only part of the plant that attains any altitude, growing between 6 inches and 2 feet in length. Small, spike-shaped leaves grow from the flower stem at regular intervals. The basal rosette of leaves withers and disappears in most species once the flower stem appears.
Nodding ladies' tresses (Spiranthes cernua) is one of the most widespread varieties in the East, occurring sporadically in most states east of the Mississippi and into Texas and Missouri. In the West, hooded ladies' tresses (S. romanzoffiana) is the prevalent species, ranging throughout the Southwestern deserts and north into Canada and Alaska. Many species, including the northern slender ladies tresses (S. lacera) and the Great Plains ladies' tresses (S. magnicamporum) are critically endangered, both from over-collection of wild habitats, as well as reduced native range.