The Sonoran Desert Florilegium

plants of the florilegium

Castilleja exserta
Owl's clover

FAMILY:  Orobanchaceae — Broomrape family

SYNONYM:  Orthocarpus purpurascens

OTHER COMMON NAMES:  Purple owl's clover, Exserted Indian paintbrush

ETYMOLOGY:  The genus Castilleja was named by the renowned Spanish botanist and priest Jose Celestino Mutis (1732–1808) to honor his countryman, botanist Domingo Castillejo (1744–1793).

The specific epithet exserta is a Latin term for something that protrudes out and beyond. In this case, the corolla protrudes slightly beyond the colorful calyx. Escobita, one of the common names, means 'little broom' and refers to the densely crowded flowers growing at the end of the plant's stems.

GEOGRAPHIC RANGE:  Found from central California to Arizona and into northwest Mexico

HABITAT: Grasslands and desert areas, 1,500–4,500'

BLOOMING SEASON:  March to May

DESCRIPTION:  Annual plant, 4–16" tall, that can grow in dense populations, forming carpets of magenta flowers in years with plentiful winter rains

Flowers to 1.25" long are reddish-purple with upper and lower lips. The upper lip has a beak-like hook at its tip that faces downward. The lower lip is tipped with white or yellow and has three swollen pouches. Bracts of the same color surrounded the flower and are divided into 5–7 one-inch long lobes. Flowers are densely crowded at the tip of the stem.

Hairy, sticky, threadlike leaves, 1/2–2" long, are divided into 5–9 linear lobes that may be tipped in purple.

NOTES:  Owl's clover is a partial parasitic, or hemiparasite, one that needs only water from its host, as it is capable of making its own food through photosynthesis. The plant invades its host through specialized structures called haustoria that function as roots, attaching themselves to the host's roots and invading its tissues. Owl's clover will grow on most desert plants, but some prove to be more beneficial hosts than others and allow more vigorous plants to grow.