Tufted Evening Primrose (Oenothera caespitosa)

Tufted Evening Primrose, Y Trail, 4/24/14, David Kenison.  Click to enlarge.

The Tufted Evening Primrose is also known as the moonrose, sand-lily, fragrant evening primrose, stemless primrose, or gumbo lily. It blooms throughout the spring, and is common in the dry foothills of the Wasatch Front and throughout the western US, at low to medium elevations.

This flower is distinguished by 4 heart-shaped petals in a bloom that is 2-4 inches across, with 8 yellowish stamen. It's unique in that it does not bloom during the day; the flowers open rapidly in the evening and often close up and turn pink after the night passes. They mature rapidly and have a short life, often a single night, before wilting. They are typically very fragrant, in order to attract the moths that pollinate them at night. They grow in clumps or tufts.

There are about 145 different species in the Oenothera genus of flowers. They are not true primroses (which are of the genus Primula), but are commonly known by that name.  Many of the flowers in the genus are brightly colored (yellow, purple, red) but desert species are often white.

These photos were taken by the author along the Y trail above Provo, Utah on 4/24/14; and along the Grove Creek trail in May and June 2013. Click on photos to view enlargements.

A beautiful regular specimen, 6/6/2013

Additional links for the Tufted Evening Primrose:
USDA Forest Service description
Utah State University Extension Services