Tufted Evening-Primrose on the slopes east of Hidden Valley

Last weekend I took one of the trails that are meandering uphill from the basement of Hidden Valley Regional Park east of Reno, Nevada. I thought I saw a collection of handkerchiefs spread over some area not very far from the trail. Close-up inspection revealed that, instead, they were flowers. It did not take very long to identify them as the Tufted Evening-Primrose (Oenothera caespitosa) of the Evening-Primrose Family (Onagraceae) [1-3].

There are many species of Oenothera [4], but this one distinguishes itself from others by its large white flowers that turn pink or rose-purple after blooming (see aged flower on left side of picture). The large flowers occur on short stems. The four petals, eight stamens and four-lobed stigma of this bisexual plant are easily recognized. The radial symmetry is less obvious as the white petals often flap and wrinkle like a tissue. Indeed, the name handkerchief plant is in use [5]. Not a nice name for a plant.

Another name, dwarf evening-primrose, seems odd for a plant that signalizes its presence by large flowers. Then, there is the name morning-lily, which, in my mind, contradicts with the name evening primrose for this plant that usually opens its flowers in late afternoon. Whatever the name, while hiking by, it gives some comfort to know that the trail side is not littered by handkerchiefs, but an interesting plant.

References
[1] Laird R. Blackwell: Tahoe Wildflowers • A Month-by-Month Guide to Wildflowers in the Tahoe Basin and Surrounding Areas. A Falcon Guide, Morris Book Publishing, LLC, 2007 ; page 56.
[2] Oenothera caespitosa Nutt. ssp. caespitosa.
[3] The Free Dictionary: Oenothera caespitosa.
[4] Various species of the Oenothera genus at CalFlora.
[5] Arches National Park: Dwarf Evening-Primrose.