White Stem Evening Primrose — February 2010

Oenothera plant

Sporting unusually large white blooms on relatively small plants, the white stem evening primrose is one of our most conspicuous spring wildflowers. This widespread plant prefers sandy soil and sunny openings of foothills or semi-desert regions. There are 34 native evening primrose species in New Mexico classified in the genus Oenothera. Linneaus adopted the Greek name for the genus of these plants, a name arising from the Greek words oinos, meaning wine, and therao, meaning to seek or to imbibe. Apparently the Greeks commonly used the root of one evening primrose species to flavor wine. The white stem evening primrose (also called prairie evening primrose, palestem evening primrose, and whitest evening primrose) is the speciesOenothera albicaulis. The species epithet derives from the Latin words albus, meaning white, and caulis, meaning stem.

White stem evening primrose is an annual with upright stems that may be branched. The stems are covered with light hairs that give the stems their distinctive whitish cast. Plants tend to grow in a spreading habit that gives them a clumped appearance, rarely exceeding 20 inches in height. The basal leaves grow to two inches in length with variable shapes and may have smooth or lobed edges. The leaves growing from the stems are long and thin, with evenly spaced short projections giving those leaves a comb-like appearance.

Oenothera flower

Flowers arise individually from upper leaf axils (where the leaf joins the stem) starting in late April and some plants may bloom sporadically throughout much of the growing season. An individual flower typically opens in the late afternoon and remains open through the night when moths, the primary pollinators, are active. Flowers tend to turn pink as they begin to wither the next morning. Each flower has four sepals that bend backwards as the flower opens and four somewhat heart-shaped white petals about one inch in length and width. Eight protruding stamens surround a single pistil that bears four conspicuous linear lobes at its tip. The fruits are cylindrical capsules containing many seeds.

The evening primrose family, Onagraceae, is well-represented in the Southwestern United States. In addition to Oenothera, there are eight other genera and about two dozen other species found in New Mexico alone. Clearly the family is well-suited to arid conditions. Native Americans are known to have prepared a poultice from white stem evening primrose used to treat swellings and for throat problems. A decoction of the roots was applied as a lotion for sore muscles. Some Apaches gathered and ate the fruits as well as collecting seeds that were ground and used as an ingredient in gravy. And the lovely white flowers were commonly used in weddings and other ceremonies. Such a bright, yet delicate blossom is indeed a fitting symbol of innocence and purity; we are most fortunate to have this reminder of nature’s grace just outside our doorstep.

© 2010 Jerry Melaragno

Downloadable pdf of this essay is here.

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