Nodding ladies’ tresses is the most common of Missouri’s eight species of ladies' tresses. In bloom, it is a slender green stalk with small white orchid flowers arranged in a spiral. The flowers are so tightly spiraled that they appear as though there are 2 or more intertwined spirals along the flowering stems — if spirals are discernible at all. The flowers are white with a pointed lip, arranged in a spiral around the stem, about ¼ to ⅜ inch long, and each points slightly downward. The flowers usually have only a faint, sweet "lily of the valley" fragrance. Blooms August–November. Stem leaves are few, very narrow, clasping the flowering stem. The basal leaves have usually disappeared before the flowers appear.
To distinguish this species from the similar Great Plains ladies' tresses (see below), note that the flowers of nodding ladies' tresses are narrowly urn-shaped, arching gently with an even curve through the length, the lip curving outward abruptly from the rest of the petals about a third of the way from the tip, and the lateral (side) sepals only slightly spreading, thus oriented parallel to the rest of the flower. The basal leaves are usually (but not always) withered away by flowering time. Also unlike Great Plains ladies' tresses, nodding ladies' tresses reproduces asexually (its seeds contain multiple embryos that do not require fertilization to be viable).
Similar species: Eight Spiranthes species grow in Missouri. Even experts can find them challenging to distinguish, as key features can include things like the relative positions of the petals and sepals and details of lip (lower petal) coloration.
- Great Plains ladies' tresses (S. magnicamporum) flowers September–November. It is scattered in the Ozark and Ozark Border divisions and lives in dolomite glades, and, less commonly, in openings of dry upland forests, fens, and limestone glades. Formerly considered a variety of S. cernua and is difficult to distinguish from it. Part of the difficulty is that S. cernua is itself quite varied. But S. magnicamporum has a strong sweet scent like freshly cut hay; its flowers are broadly urn-shaped, curving mostly near the base, with the lip still diverging from the upper sepal and lateral petals about a third of the way from the tip; however, the lateral sepals are spreading, the tops arching upward and angled away from the rest of the perianth (petals). The basal leaves have withered away by flowering time. This plant usually reproduces sexually, via pollination by bees.
- Shining ladies' tresses or yellow-lipped ladies' tresses (S. lucida) flowers in May–June and is our earliest flowering Spiranthes. (The others bloom in late summer and fall.) It is restricted to fens and seeps in the Ozark and Ozark Border regions. It has a bright yellow area on the lip of the flower and has broad, shiny leaves. The flowers appears as though in 2 or more ranks along the stems.
- Spring ladies' tresses or twisted ladies' tresses (S. vernalis) flowers June–September. It is widely scattered, mostly south of the Missouri River, and lives mostly in upland prairies and similar habitats. Growing up to 40 inches tall, it is our tallest Spiranthes, and the flowers are clearly in a single spiral. It flowers earlier than the other species that have flower spikes in a single spiral.
- Slender ladies' tresses (S. lacera) flowers August–October. It is scattered nearly statewide except for the far northwestern corner. It lives in dry upland forests, upper slopes of bluffs, dry upland prairies, mostly on acidic substrates; also in old fields and a variety of other disturbed, open situations, especially in dry, cherty or sandy soils. It is a slender, delicate plant with a thin stem. The flowers appear as a single spiral, although sometimes no spiral is discernable. Unlike the closely related little ladies' tresses (S. turberosa), it has a green spot on the lip of each flower and has somewhat longer, sparsely glandular-hairy flower spikes. Of the two, S. lacera is generally taller, more slender, and has a more regular, more graceful spiral of flowers.
- Little ladies' tresses (S. tuberosa) flowers August–October. It is scattered, mostly south of the Missouri River, and lives in upland forests, bluff tops, mostly on acidic substrates; also in old fields, dry roadsides, often in dry, sterile, cherty of sandy soils; sometimes also in lawns. The flowers appear as a single spiral along the flowering stem. Similar and closely related to slender ladies' tresses (S. lacera), but little ladies' tresses has the lower lip all white, and the center axis of the flower spike is glabrous (smooth; hairless), not glandular-hairy. S. tuberosa and S. lacera are sometimes found growing near each other.
- Oval ladies' tresses (S. ovalis var. erostellata) flowers September–October. It is uncommon and widely scattered in Missouri. It lives in wet to moist bottomland forests, moist upland forests, and less commonly in shaded portions in old fields. Grows to 16 inches high, and the 2 or 3 hairless, dark green, grasslike basal leaves are present at flowering time; the broadest portion is at the outer tip of the leaf, not at the base. The flowers are crowded in 2 or more ranks or intertwined spirals; the flower spike is covered with downy hairs.
- Greenvein ladies' tresses (S. praecox) blooms in our state in late May–early June. It is a species of conservation concern in Missouri and is known from only one location in Stoddard County, along the edge of a wetland. It was first reported for our state in 2015. It occurs mostly in the Atlantic Coastal Plain and southeastern United States, and Missouri represents a northwestern limit of the overall range. Unlike the similar spring ladies' tresses, which also has flowers clearly in a single spiral and blooms about the same time, the flowers usually have green veins or streaks on the lower lip, and the growing stalk is only sparsely hairy.
Height: 4–20 inches.
Scattered nearly statewide, but most common south of the Missouri River.
Habitat and Conservation
Occurs in glades, upland prairies, and old fields on acidic substrates; also in acidic soils in moist forests, thickets, and open stream valleys. Rarely also found on floating mats in sinkhole ponds.
Status
In Missouri, this is one of the most common and widespread orchids in the genus Spiranthes.
The orchids are one of the largest families of flowering plants, but most live in the tropics. Missouri has about 36 orchid species; globally, there are about 15,000.
Many of Missouri's orchids occur in small populations and are declining due to habitat changes (soil moisture, light levels, density of surrounding plants, and so on). They do not transplant well, so take photographs instead!
Human Connections
The common name of "ladies' tresses" apparently arose because the spiral arrangement of the flowers resembles long, braided or curled hair. One of the reasons many common names of plants have endured for so long is their poetic or colorful way of describing some aspect of the plant; they are easy to remember!
Botanists debate the classification of orchids, and genetic testing has helped define the boundaries between species and genera.
Morphology (the form and shape of various plant parts) can be deceiving in this group. For example, the species of Spiranthes in Missouri all have the flowers arranged in a single spiral. However, in some of them, the spiral is so tight, and each loop of flowers around the axis occupies so little vertical space, that the overall appearance presents the illusion of two or more vertical ranks or intertwined spirals. Sometimes, in such plants, the spiral nature of the flowers is not discernable at all.
Ecosystem Connections
Orchids are famous for their outrageous diversity in flower shapes. Their weird flower parts — lips, columns, saclike pollen masses, sticky pads, and more — are adaptions to enable pollination by various insects. The spiral pattern of ladies' tresses is thought to encourage pollination by bees. Nodding ladies' tresses, however, has gone a step further and reproduces asexually (its seeds contain multiple embryos that do not require fertilization to be viable). This ability to create seeds without pollination or even fertilization might help explain this plant's success as one of our most common and widespread orchids.
Most of the species in genus Spiranthes are pollinated by various bees, ranging from bumblebees to honeybees and smaller, native bees. The spiral pattern typical of Spiranthes orchids is thought to be an adaptation to bee pollination. Cora Steyermark observed that the flowers open "first at the bottom of the spike. The bee that fertilizes the orchid starts with the older flowers at the bottom and spirals up with the flowers around the spike, like the little brown creeper bird, following the flowers upward to the top, picking up pollen on the way up. Then again, like the brown creeper, the bee flies to the lower flowers of the next orchid plant spreading pollen" as it again spirals upward.
Orchids are notoriously difficult to propagate horticulturally, because in addition to their unusual and exacting relationships with pollinating insects, their tiny seeds must also germinate in an appropriate habitat and in the presence of special types of symbiotic fungi, whose netlike filaments in the soil increase the embryonic orchid plant's ability to get moisture and nutrients. Unlike acorns or butterbeans, orchid seeds are tiny (vanilla is an orchid, so think of the tiny seeds in a vanilla "bean"). These little seeds are not equipped with energy reserves to support early root, stem, and leaf growth. They require the fungi to supplement their nutrients, or they will soon perish.
