one-sided wintergreen

not listed

N5? - Secure

SNR - Unranked

not listed

FACU - Facultative upland

FAC - Facultative

FAC - Facultative

One-sided wintergreen is a common but often overlooked plant in northern and mountain forests. It is native, widespread, and common across the Northern Hemisphere. In the United States it is common in New England, the Upper Midwest, and the West, absent from the South and Lower Midwest. In Minnesota it is very common in the Arrowhead and north-central regions, less common in the Metro and southeast regions, and absent from the southwest. It is found in deciduous, coniferous, and mixed forests, and in bogs. It grows in dry to moist soil under full to partial shade. In Minnesota it is found mostly on moist, mossy forest floors. It obtains about half of its nutrients from the underground fungal (mycorrhizal) network that assists other plants in absorbing nutrients from the soil.

One-sided wintergreen is an erect, perennial, long-lived forb that rises on a single stem from a forking, underground, horizontal stem (rhizome). It can be 4¾″ to 13″ (12 to 33 cm) tall, but is usually less than 7⅞″ (20 cm) in height.

The leaves are evergreen, ¾″ to 1⅞″ (20 to 47 mm) long, and ¼″ to 1⅛″ (7 to 28 mm) wide. They are firm and sometimes have an almost leathery texture. They appear basal, rising from the rhizome, but are actually clustered on the stem near the base. They appear to be in whorls, emerging from the same point on the stem, but are actually alternate or in pseudowhorls, very closely spaced but emerging at separate points on the stem. There are usually 2 to 4 pseudowhorls, sometimes just 1. Each leaf is on a hairless, ⅛″ to ¾″ (4 to 20 mm) long stem (petiole). The petiole is channeled above. The leaf blade may be egg-shaped or broadly egg-shaped, widest near the base; elliptic, widest at the middle; or nearly circular. It is rounded to narrowly angled at both ends. The upper surface is shiny, green, and hairless. The lower surface is dull, light green, and hairless. The margins are flat, rarely somewhat rolled toward the underside. It may be untoothed or have fine rounded teeth. It does not have sharp teeth.

The stem may be erect or lay on the ground with just the tip curved upward (decumbent). There is no visible point where the short stem ends and the long inflorescence stalk (peduncle) begins. Both are hairless and green or slightly reddish. The stem is unbranched, leafy, and smooth to the touch. The peduncle is unbranched and leafless but usually has minute, pimple-like protuberances (papilla), especially dense toward the top. There are usually 2 to 5 small modified leaves (bracts) on the peduncle, but these may be absent. The bracts are narrowly or broadly lance-shaped, ⅛″ to ⅜″ (3 to 9 mm) long, and 1⁄32″ to 1⁄16″ (1 to 2 mm) wide.

The inflorescence is a ¾″ to 2″ (2 to 5 cm) long, unbranched cluster (raceme) of flowers at the end of the stem. There are usually 6 to 20 flowers but there may be as few a 2 or as many as 29. They hang downward from one side of the arcing tip of the peduncle.

Each flower is ¼″ to ⅜″ long, bell-shaped, and as long or longer than wide. It hangs from a ⅛″ to ¼″ (3 to 7 mm) long flower stalk (pedicel). At the base of each pedicel, but not attached to the pedicel, is a scale-like, awl-shaped or more or less lance-shaped bract. The bract is about the same length as the pedicel. There are 5 outer floral leaves (sepals), 5 petals, and 10 stamens, and 1 style. The sepals are fused just at the base then broadly separated into 5 broadly triangular to egg-shaped lobes. They are green but may have white or pinkish margins. The petals are white, 3⁄16″ to ¼″ (4.5 to 6.0 mm) long, and ⅛″ (3 to 4 mm) wide. The stamens protrude just beyond the petals. The style is green, stout, and long, protruding far beyond the petals.

The fruit is a flattened globe-shaped, ⅛″ to 3 ⁄16″ (3 to 5 mm) long, ⅛″ to ¼″ (4 to 6 mm) in diameter capsule. When in fruit the peduncle straightens and elongates and the pedicels straighten so that the capsules are stiffly held more or less parallel to the ground. The infructescence (all of the fruits) is up to 3⅛″ (8.5 cm) long.

4¾″ to 7⅞″ (12 to 20 cm)

White

Dry to moist. Deciduous, coniferous, and mixed forests; and bogs. Full to partial shade.

June to July

One-sided wintergreen grows in the often deep shade of northern forests. In 2007 it was discovered that it obtains about half of its nutrients from the underground fungal (mycorrhizal) network that assists other plants in absorbing nutrients form the soil.

Sources

2, 3, 4, 5, 7, 28, 29, 30.

Native

Common

Some authorities, including GRIN, place the tribe Pyroleae in the subfamily Monotropoideae. Others place it in the subfamily Pyroloideae. The Angiosperm Phylogeny Website, which should be the last word on naming of North American plants, places Pyroleae in the subfamily Pyroloideae.

One-sided wintergreen was formerly placed in the genus Pyrola, and Pyrola was formerly placed in the family Pyrolaceae. In 2002, Pyrolaceae and four other families were placed in the heath family (Ericaceae). This species was placed in the new genus Orthilia based on the one-sided inflorescence and the longer, bell-shaped flower. It remains the only species in that genus.

Flowering plant

Inflorescence

Fruiting pant

Leaves