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Plant of the Week

Macfarlane's four-o-clock (Mirabilis macfarlanei Constance & Rollins)

By Russell Holmes

Macfarlane's four-o-clock is a member of the Nyctaginaceae (Four-o-clock family) which contains approximately 300 species worldwide occurring mostly in tropical and subtropical regions. There are 88 species recorded in North America. A few species in the family are popular ornamentals. Other species are sources of compounds that have medicinal value. Macfarlane's four-o-clock is a federally threatened species endemic to northeast Oregon and Northern Idaho. Seeds of the species have been collected and placed in long-term storage in the Center for Plant Conservation national collection of endangered plants as a conservation measure.

Macfarlane's four-o-clock is a stout perennial forming large clumps 6 to 8 dm (24 to 32 inches) in diameter and 6 to 10 dm (24 to 40 inches) tall. Stems are decumbent or ascending, branched and covered with short, fine hairs. Leaves are opposite with circular to ovate fleshy blades 4 to 7 cm (1.6 to 2.8 inches) long and petioles 5 to 20 mm (0.2 to 0.5 inches) long. Flower clusters form in the upper axils or on terminal stalks. Flowers are rose-purple and broadly funnel form. Stamens exceed the perianth segments and support yellow anthers. Plants bloom in May.

Macfarlane's four-o-clock grows on rockslides, canyon walls, and sandy to gravelly talus slopes. Elevation ranges from 300 to 900 m (980 to 2050 feet) Associated species include beardless bluebunch wheatgrass (Pseudoroegneria spicata), cheatgrass brome (Bromus tectorum), Idaho fescue (Festuca idahoensis), and sweet clover (Melilotus).

Macfarlane's four-o-clock habitat. Macfarlane's four-o-clock habitat. Photo by Russell Holmes.

Macfarlane's four-o-clock habitat. Macfarlane's four-o-clock habitat. Photo by Russell Holmes.

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Related Species

Map of the North America showing areas colored green where the species may be found. Range map of Macfarlane's four-o-clock. States are colored green where the species may be found.

Macfarlane's four-o-clock flower. Macfarlane's four-o-clock (Mirabilis macfarlanei) flower. Photo by Russell Holmes.

Macfarlane's four-o-clock flowers. Macfarlane's four-o-clock (Mirabilis macfarlanei) plant. Photo by Gene Yates.

Macfarlane's four-o-clock plant. Macfarlane's four-o-clock (Mirabilis macfarlanei). Photo by Russell Holmes.

Macfarlane's four-o-clock habitat. Macfarlane's four-o-clock habitat. Photo by Gene Yates.