Plant Story--Handsome Ten-Petal Blazingstar, Mentzelia decapetala

The blazingstars, genus Mentzelia, are an American group, but especially western North American. Some species are found in the Caribbean, Central, and South America but 85 of the approximately 95 species are North American. If you live in the eastern half of the United States, you can be forgiven for never having heard of this group, because only three species have ranges east of the Mississippi. (Those are a Florida endemic and two found east to Illinois). Colorado has 25 species, almost all in the western half of the state, west of the Rocky Mountains; only four species grow on the eastern plains. They are in the small plant family Loasaceae, the blazingstar family.

ten-petal blazingstar, Mentzelia decapetala, at night

Mentzelia decapetala, called ten-petal blazingstar, is the showiest of them. It grows to 3 feet tall, with flowers about 4" across, the petals white, stigma and stamens yellow. The flowers are very handsome. They open after dark, the flowers fading after midnight. 

Unlike most of the Mentzelia species, ten-petal blazingstar is found east of the Rocky Mountains, from Manitoba, Minnesota, Illinois, Kansas, Oklahoma and Texas, then over the Rockies, west to New Mexico, Utah and Montana, and Alberta. It grows in drier grasslands and on gravelly slopes and, while it is not rare, is not common; you have to be lucky to encounter a stand of them.

ten-petal blazingstar
Mentzelia decapetala

Ten-petal blazingstar does not have a well-defined common name. This name, ten-petal blazingstar, is used by the Flora of Colorado and the USDA Plants data base. The Flora of North America gives gumbo-lily as the common name. When I google that, I get an evening primrose, Oenothera caespitosa, not a Mentzelia, so I think that is an error in the Flora of North America. Searching for common names in my collection of plant books and online, I find it as sand lily, but that also refers to Mentzelia nuda (smaller, more common) and Leucocrinium montanum (an unrelated plant). An obvious common name based on the scientific name is ten-petal mentzelia. In addition, I found these common names as well: ten-petalled western star, eveningstar flower and large eveningstar, chalk lily, candleflower, and prairie lily.

Stickleaf is another common name for the plains Mentzelia species M. decapetala and M. nuda; both have hairs on the leaf that cling, ten-petal blazingstar sticking a little when fresh, better when dry, while the leaves of bractless blazingstar, M. nuda, stick on to most fabrics whether the leaves are green or dry. Leaves that cling occur in other species of Mentzelia as well. Thus, a common name for M. decapetala is ten-petal stickleaf. It certainly has "scratchy" leaves. 

Close-up of ten-petal blazingstar leaf. The white lines are leaf hairs
that make it feel very coarse. 

The genus Mentzelia is named for the German botanist Christian Mentzel (1622-1701). The species epithet decapetala means "ten petal." The implication of a species epithet is that is describes something distinctive about the organism. Mentzelia decapetala can have 10 petals, but also 8 or 9, and several of its relatives have a similar petal count. A disappointing choice.

Sater in late August in Montana and Brown and Kaul in late August in Nebraska saw the big buds start to open in the twilight and become fully open about sunset. In my observations (Colorado, August 1)  tho, the flowers did not fully open until it was very dark; perhaps opening varies a little with the date, plant health, or light quality. (In the related Mentzelia nuda, I found that the flowers opened rather precisely about 4 pm during the main part of the flowering season but by September could be earlier or later.) Newly-opened flowers have a distinct pleasant fragrance. Brown and Kaul observed the flowers to close about midnight. Gorgeous, aren't they?

ten-petal blazingstar, Mentzelia decapetala flowers

I did not see any pollinators, but it was very dark and I was not prepared to stay out for hours. Reported pollinators are bumblebees, flies, and several kinds of moths; from the color and when the flowers open, I would predict that the best pollinators are moths, but no one has seriously studied pollination in ten-petal blazingstar. Brown and Kaul saw seed production in the greenhouse, without pollinators, so presumably ten-petal blazingstar can and does self-pollinate.

Like many wild night-blooming plants, the botanists that wrote about ten-petal blazingstar saw dried pressed flowers or came by in cool conditions when the flowers stayed open later, so did not realize it was night blooming. Only a few of my "Flowers of the..." books mention that it opens at night.

Also not obvious in the plant books is that these plants are monocarpic: they die after flowering. The books say "biennial or perennial" and that is true. In the dry grasslands, they will take several years to grow big enough to flower, making them perennial. But most perennial plants return from the roots in the spring to flower again next year. These will not, half of the two-year-old plants I am growing, flowered in this their second year (making them biennials). These have no green leaves left, only developing seed pods; flowering consumed the leaves and much of the storage in the root. Meanwhile, the ones that did not flower have big healthy green leaves even though it is October.

non-flowering plant, ten-petal blazingstar

I did a multi-year study of bractless blazingstar, Mentzelia nuda, partly to show that it was not monocarpic--did not die after flowering--as one of my colleagues had asserted. That species will flower repeatedly, for at least six years. Whether ten-petal blazingstar can repeatedly flower if growing in the right conditions, I can't say, but mostly being monocarpic or not monocarpic is a fixed characteristic within a species since strong selection for whichever pattern of blooming works best in the environment quickly eliminates the alternate flowering pattern, so I do not expect resprouting of plants that flowered. 

(For the record, I see no post-floral nectaries on ten-petal blazingstar, unlike bractless blazingstar). 

The first collection of ten-petal blazingstar for western science was by Lewis of the Lewis and Clark Expedition in 1804.

I can find no Native American uses listed for ten-petal blazingstar, but west of the Rockies, leaves other species of Mentzelia were collected to make washes for skin ailments, the roots used in laxatives, and the seeds dried and roasted for food (eaten as flour, or mush, or as "peanut butter.") Probably those uses apply to ten-petal blazingstar, but possibly not, perhaps it is too low in medically active chemistry to make a decent medicine or the seeds do not taste good. Plants in the same genus can be very different. 

Some of the older literature I read did not convince me that they distinguished Mentzelia decapetala and M. nuda properly. In my experience M. decapetala is bigger, opens at night, has yellow stigmas and stamens, and is found in disturbed and rocky sites, while M. nuda is smaller, opens at 4 pm (full daylight in summer), has white flowers with white stigmas and stamens, and favors disturbed sandy sites. (About bractless blazingstar Mentzelia nuda link). However, both species have native ranges across a dozen states, so growing conditions differ and so could the plants. Still, it feels like more people should carefully study and write about species of Mentzelia. 

buds

flowers

A really interesting plants, with scratchy leaves and handsome flowers!

Comments and corrections welcome.

References

Brown, D.K. and Kaul, R.B. 1981. Floral structure and mechanism in Loasaceae. American Journal of Botany 68(3):361-372.

Hufford, L., J.J. Schenck, and J. M.Brokaw. 2020. Mentzelia Linnaeus  Flora of North America link Accessed 10/6/24.

Kaul, R.B., D. Sutherland, and S. Rolfmeier. 2011. The Flora of Nebraska. University of Nebraska Press, Lincoln.

Keeler, K.H. 1981. Function of Mentzelia nuda (Loasaceae) postfloral nectaries in seed defense. American Journal of Botany 68(2):295-299.

Keeler, K.H. 1987. Survivorship and fecundity of the polycarpic perennial Mentzelia nuda (Loasaceae) in Nebraska Sandhills prairie. American Journal of Botany 74(6):785-791. 

Moerman, D. E. 1998. Native American Ethnobotany. Timber Press. Portland, Oregon.

Sater, S. 2022. Fly killer, bee lover: the secret life of Mentzelia decapetala. Wild with Nature link

Kathy Keeler

A Wandering Botanist

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