Dwarf Owl’s Clover

Leonard and I also observed dwarf owl’s clover (Triphysaria pusilla) on the top of Lower Table Rock (near Medford OR) in April.

This annual native was originally in the genus Orthocarpus and only recently was moved to Triphysaria. The genus name is from the Greek and means “having 3 bladders” in reference to three pouches on the lower lip of the flower. This plant only grows to a height of about 3 inches atop Lower Table Rock and grows only slightly taller throughout its range. Its flowers are also tiny and almost hidden. Thus the species designation, pusilla, meaning “small, weak or insignificant” in Latin is appropriate.

Dwarf owl’s clover is hemiparasitic. This means that the plant has chlorophyll and can photosynthesize, yet it also maintains a connection with the roots of a host plant through which it derives minerals, other nutrients or water. A structure which grows in and around the host’s root hairs, the haustorium, secures the dwarf owl’s clover to the host plant. An intrusive keel-like part of the haustorium penetrates to the hosts vascular tissue and provides a conduit for transfer of nutrients or water.

The dwarf owl’s clover stem is erect or decumbent. Each plant has a main stem and several branching stems. The vegetation is purplish brown and covered with small, rough hairs. The leaves are three-lobed.

Inconspicuous flowers arise in the bract axils and are hidden by the bracts. (A bract is a modified leaf at the base of an inflorescence or flower.) The flower has a hairy, lobed calyx (sepals) and a two-lipped corolla (petals collectively). The lower lip of the dwarf owl’s clover flower has three pouches. The upper lip is a hood over the 4 anthers (only one pollen sac per anther) and a style.

The seeds are ovoid and dark brown.

Dwarf owl’s clover is found in British Columbia, Washington, Oregon and California at lower elevations. The habitat of this Broomrape Family member is moist, open areas such as meadows, pastures and grassy slopes.

My next post will be a plant that is found only at the Table Rocks – table rock meadowfoam (Limnanthes pumila ssp pumila).

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2 Responses to Dwarf Owl’s Clover

  1. Lin Erickson says:

    Very interesting plant!

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