Oenothera cespitosa

Oenothera cespitosa
Oenothera caespitosa subsp. marginata
Scientific classification
Kingdom:	Plantae
Clade:	Tracheophytes
Clade:	Angiosperms
Clade:	Eudicots
Clade:	Rosids
Order:	Myrtales
Family:	Onagraceae
Genus:	Oenothera
Species:	O. cespitosa
Binomial name
Oenothera cespitosa Nutt.
Subspecies[1]
O. c. subsp. cespitosa O. c. subsp. crinita O. c. subsp. macroglottis O. c. subsp. marginata O. c. subsp. navajoensis
Synonyms[1]
Pachylophus cespitosa

Oenothera cespitosa, known commonly as tufted evening-primrose or fragrant evening-primrose, is a perennial plant of the genus Oenothera native to western North America from the western edge of the Great Plains and all parts of the Intermountain West in a wide range of dry habitats. Its flowers are open at night and fade by the next day. The species is cultivated in gardens, particularly in its native range.

Oenothera cespitosa is a low growing herbaceous plant that grows from a substantial taproot. Plants can have stems that can reach as much as 40 centimeters (16 in) in length or lack stems entirely. When present the stems are quite variable. They might be branched near the base or unbranched and are usually covered in fine glandular hairs, but can also be hairless on occasion.^[2] New shoots are sometimes produced the plant's slender, spreading side roots.^[3] Though the rest of the plant is herbaceous the caudex is woody.^[4]

The leaves grow together in a rosette.^[4] The leaves are sometimes hairless, but are more often puberulent, covered in small fine hairs, to villous-hirsute, covered in long hairs with a fine to coarse texture. They tend to be especially hairy on the leaf edges.^[5] Leaves range from 1.7 to 36 centimeters in length, but are usually shorter than 26 cm. They can be 0.3 to 6.5 cm wide, but are more commonly 0.5 to 4.5 cm. Normally they are oblanceolate to rhombic or spatulate in overall shape, but highly variable. The edges are irregualarly toothed, wavy, or even lobed and are narrowly pointed or rounded at the ends.^[2]

The four-petaled white flowers open at in the afternoon to evening hours and remain open all night.^[6][2] The flowers wilt the next day when it becomes hot.^[6] The fading flower petals darken and turn light rose to dark rose purple.^[2] Pressed flowers are generally darker than those found on plants in nature.^[5] Open flowers produce a strong, sweet floral scent accompanied by a slight smell like rubber. Each petal can measure 1.6 to 6 centimeters (0.6 to 2.4 in) long, though more often 2–5 cm (0.8–2.0 in). A notch in the center of the petal may make them obcordate, heart shaped with the point attaching to the plant, or they can be obovate, shaped like a teardrop.^[2]

Each flower bud develops by itself in a seperate leaf axil, the crevice formed where the leaf's base attaches to the plant.^[3] Buds are closed by four sepals that measure 1.5 to 5.5 cm (0.6 to 2.2 in) long and that curve backwards sepeartely when the flower is in bloom.^[7] On any evening during the bloom season each stem may produce one to six flowers.^[2] Depending on elevation the blooming season can start as early as April and end as late as August.^[5]

Oenothera cespitosa was described and given its scientific name by Thomas Nuttall sometime prior to August 1813.^[8] It has five accepted subspecies according to Plants of the World Online (POWO).^[1] However, according to the World Flora Online three of these are botanical varieties marked with asterisks in the following list.^[8]

• Oenothera cespitosa subsp. cespitosa*
• Oenothera cespitosa subsp. crinita (Rydb.) Munz*
• Oenothera cespitosa subsp. macroglottis (Rydb.) W.L.Wagner, Stockh. & W.M.Klein
• Oenothera cespitosa subsp. marginata (Nutt. ex Hook. & Arn.) Munz*
• Oenothera cespitosa subsp. navajoensis W.L.Wagner, Stockh. & W.M.Klein

According to POWO it has 40 synonyms of the species or one of its five subspecies.^{[1][9][10][11][12][13]}

The species name, cespitosa, means "growing in a tuft".^[3] The species is similarly known by the common names tufted evening-primrose or white-tufted evening-primrose.^[14][6] They are also known as gumbo evening-primrose.^[15]

It shares other common names with many other plant species. Along with Oenothera stricta it is called fragrant evening-primrose,^[4][16] together with Oenothera primiveris is called desert evening-primrose,^[17][18] with Oenothera tetraptera is called white evening-primrose,^[3][19] and with both genus Cistus and Helianthemum it is called rock rose.^[17][20]

They are occasionally called sand lilies or morning-lily, despite it not being part of the lily family.^[21][22] There are many other plant species known as sand lily.^[23]

Tufted evening primrose is native to western North America from southern Canada to northern Mexico. In Canada it grows in just three provinces, Alberta, Manitoba, and Saskatchewan.^[1] In Mexico it is found in four states, Baja California, Baja California Sur, Chihuahua, and Sonora.^[24]

The greater part of its range is in the western United States.^[1] There it grows in the interior areas of Washington and Oregon eastward through Idaho and Montana to encompass half of North and South Dakota. Southward it grows in just four far western counties of Nebraska, but in almost all of Wyoming, Colorado, and New Mexico. It is listed as growing in Texas by the Natural Resources Conservation Service, but without a specific location. It also native to all of Arizona, Utah, and Nevada, but only to a few dry areas of northeastern California and its southern deserts.^[14]

The species grows in a wide range of habitats including grasslands, desert scrub, piñon–juniper woodlands, Arizona chaparral, and into mountain conifer forests.^[2] Very rarely, they can be found above timberline. They are particularly noted for growing in disturbed habitats such as next to roadways as well as on talus slopes and in sandy areas.^[25][26] Usually they grow in dry habitats.^[5] They regularly grow at elevations of 800 to 3,370 meters (2,620 to 11,060 ft) and rarely can grow as low as 450 m (1,480 ft).^[2]

The plant is a larval host to the white-lined sphinx moth.^[27]

Oenothera cespitosa is dependent on hawkmoths, including the five-spotted hawkmoth (Manduca quinquemaculata) for pollination.^[28]

Oenothera deltoides is very similar, with short stems and slightly smaller flowers.^[26]

Tufted evening-primroses are grown in rock gardens, moon gardens,^[29] and in native plant gardening.^[25] They are valued for attracting hawk moths, for their pleasant scent, and long blooming season of about six weeks in early to late summer.^[30] The plants require good drainage.^[27]