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Idaho Mountain Wildflowers

Blazing-star Family, Loasaceae

The blazing star family is small, made up of twenty genera and about 320 species. While many species occur in the United States, especially in the southern and southwestern states, the family is represented in Idaho by only four species. Three of these--all grow to the montane zone or higher--are shown below. (The fourth species, Mentzelia dispersa S. Wats., is one that we have not yet encountered.) The blazing-star family has little economic importance other than the use of some of the plants as cultivated ornamentals. As with various evening primroses (Onagraceae), the flowers open in the evening, are pollinated by night-flying insects, and then fade away during the day.

Blazing star, Mentzelia laevicaulis Douglas ex Hook.) Torr. & A. Gray (left) is relatively tall with rough foliage. Five of its many stamens are flattened and petaloid, although they are not nearly as large as its five true petals. This blazing-star grows in Montana, Wyoming and Colorado, west to British Columbia and the three coastal states. It is often seen growing on gravelly road embankments as high as the subalpine zone. Because its flowers are showy, the plants are sometimes cultivated as a garden ornamentals in dry environments. The genus is named for German botanist, Christian Mentzel (1622-1701).

Ten-petaled blazing star, Mentzelia decapetala (Pursh) Urban & Gilg ex Gilg (right). The large, ten-petaled (decapetala) blazing star is not a flower easily missed. It blooms late in the day, is moth- pollinated at night, and closes early in the morning. During the rest of the day the plants look like tall, rough-leaved weeds. The ten- petaled flowers include five true petals and five inner modified stamens (“staminodes”). Lewis and Clark collected this new-to-science plant in August, 1804, near today’s Homer, Nebraska. Primarily a Great Plains plant, it grows from the Mississippi River west to Idaho where it occurs in scattered locations, growing on south-facing gravelly slopes to fairly high elevations.

White-stem mentzelia, Mentzelia albicaulis (Douglas ex Hook.) Douglas ex Torr. & A. Gray (left). Because this plant is so unlike the other two Loasaceae shown here, and because its flowers--at first glance, at least--look like plants in the rose family, potentillas especially, identifying it as a mentzelia may be difficult on first encounter. While described as a desert or foothill plant, we have seen the small-flowered mentzelia flourishing at nearly 7000 feet in the mountains of Central Idaho. It grows throughout the West, from Arizona, New Mexico and Texas to the Canadian province of British Columbia. The species name albicaulis means "white stem."

Nevada mentzelia, Mentzelia dispersa S. Watson (right). The two plants shown on the left and right, are so unlike the gaudy mentzelias shown above that it is hard to believe that they are in the same genus. The Nevada mentzelia differs from the somewhat similar white-stem plant in being less hairy and having entire (no lobes), lanceolate leaves; their small flowers are rather similar. This plant has much the same distribution as the other, although it does not extend into the states of the Southwest. It too grows as high as the montane zone in our mountains.

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