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Idaho Mountain Wildflowers

The Evening Primrose Family, Onagraceae

The evening primrose family consists of seventeen genera and 650 species. Although representatives are found world-wide, they are especially abundant in the Americas. Plants from several genera are cultivated as garden ornamentals, examples include North American species of Clarkia, Epilobium, Gaura and Ludwigia, as well as cultivars of Fuchsia from Central and South America. The family’s flowers are radially symmetrical with four petals, four sepals and four, or occasionally eight, stamens. In many species, the petals and sepals are joined into a long narrow tube that looks more like a stem than part of the flower. The Onagraceae are well represented in our mountains, especially by Epilobium species at higher elevations. The common name, “evening primrose family,” reflects the tendency of various short-blooming flowers in this family to open in the afternoon and fade away the following day, an understandable trait because they depend on night-flying  hummingbird moths for pollination. Some of the species that flower only for an evening open suddenly, sometimes in a few seconds.

Fireweed, Chamerion angustifolium (L.) Holub. (left, right, above) Because the common fireweed prefers disturbed ground it is considered a weed, an undeserved reputation at least in our mountains. It spreads by underground stems reclaiming ground after wildfires (above). As reforestation proceeds, fireweeds are replaced by other flora. Four-petaled flowers and a stem-like flower tube are family characteristics. The tube contains the ovary; this matures into a long pod-like seed capsule. They have recently been reclassified from genus Epilobium to Chamerion, a pre-Linnaean name for the fireweed (or rosebay willow-weed as it is known in Europe).

Red willow-herb, Chamerion latifolium (L.) Holub (left). The willow-herbs are named for the resemblance of their leaves to those of the willows. Those shown here are summer- blooming plants; all grow as high as the subalpine zone. The red (or dwarf) willow-herb is found only on the sandy banks and sandbars of mountain streams. It is a lovely flower whose four red petals alternate with color-matched, lanceolate sepals. The name, latifolium, means “wide leaf” although the leaves are wide only in comparison to those of the fireweed shown above.

Common willow-weed, Epilobium ciliatum Raf. var. glandulosum (Lehm.) Dorn (right), has loose clusters of tiny (less than 1/4 inch), bell-shaped flowers with four deeply notched petals. It blooms from July to mid-August along mountain streams and in other moist situations. Its stems and foliage feel sticky hence the name glandulosum (a “gland,” botanically implies a secreting cell with sticky secretions). Note the long tubular “stem” that houses an ovary; this matures into a pod-like seed capsule.

Autumn willow-weed, Epilobium brachycarpum C. Presl (left, right) is a mid- to high altitude plant that blooms in August. It is a common, spindly, windblown plant that grows on bare, dry ground. Its many tiny pink to white flowers have four deeply notched petals lined with reddish veins. If you try to photograph the plant you will find that it is in constant motion, waving with the slightest breeze. Formerly classified as Epilobium paniculatum Nutt. ex Torr. & A. Gray, its new species name, brachycarpum, means “short-fruit.”
Rock-fringe, Epilobium obcordatum A. Gray (left), is a showy, bright pink plant that flowers in July and into August. It is quite localized in its growth preference. A subalpine small-leaved creeper, it grows in rocky crevices, or at the base of south-facing rocks and cliffs. The flowers are large—up to two inches in diameter—with four, bright pink, heart-shaped (obcordatum) petals, eight stamens and a long dependent style tipped with a cross-shaped stigma.

Alpine willow-weed, Epilobium lactiflorum Hausskn. (right). The four-petaled flowers of the alpine willowweed are tiny, as is the plant overall. Until recently its species name was Epilobium alpinum L., but because of confusion with other species of the same name, it has been reclassified as Epilobium lactiflorum. Although its species name means milky- flowered, its flowers may range in color from pure white through white with pink veins (as in the one shown here), to fully pink or even rose. Any small white to pink, high ranging epilobium with slightly serrated leaves will most likely be this plant.

Spreading groundsmoke, Gayophytum diffusum  Torr. & A. Gray var. diffusum (left, right, above). While hiking our trails in mid- to late summer, one often sees this wispy plant growing on dry ground. Dense clusters about a foot high are made up of many thin, branched stems (above). These bear small white-to-pink flowers less than 1/4" wide. Although it takes magnification, one can see that the four-petaled flowers have sharply reflexed (turned back) bracts below the petals (left). The stems also bear tiny lanceolate leaves and sausage-shaped, seed-bearing fruit. The pods split open when ripe to release plumed seeds (right). This weedy little plant is common in the western part of the United States and in Canada . The genus is named for French  naturalist Claude Gay (1800-1873), best known for his comprehensive flora of Chilean plants.

A smaller variety (not shown here), Gayophytum diffusum var. parviflora Lewis & Szweykowski, is only about 6" high and its tiny flowers are less than 1/8" an inch across. The two varieties are similar except fot their size.

Ragged robin, Clarkia pulchella Pursh. The ragged robin (also known by many other common names including the now preferred “pink-fairies”) is a plant of the Northwest, best seen growing wild. Meriwether Lewis collected it near today’s Kamiah, Idaho, on June 1, 1806. It was, as Lewis recognized, an oddly configured little plant, one then unknown to science. It is interesting both for its unusual appearance, and also because it is the only plant of those that the expedition collected that bears William Clark’s name. The plant defined the genus Clarkia; there are now about forty species. The plant turns up in unexpected places in eastern Oregon and western Montana as well as in Idaho.

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