Owl-clovers are native, annual herbs, mostly hemiparasitic, smooth to slightly glandular-hairy. The stems are slender, erect, about 10-40 cm tall, usually simple. The flowers are arranged in a narrow spike, supported by green bracts which are leaflike below and progressively reduced and 3-lobed upwards. The flowers are bright lemon yellow and bloom a few at a time. The shape of the flowers is strongly two-lipped. The calyx is at least partially united, tubular and bell-shaped, 6-8 mm long, 4-lobed. The corolla is yellow, elongated and narrow, minutely hairy, forming an upper lip which is hooded, erect and straight, beak-like, with its lobes united to the tip and enclosing the anthers. The lower lip equals the upper lip in length, it's minutely 3-toothed. The flowers have 4 stamens and stigmas which are united and in a dense cluster. Leaves are rough-hairy, alternate, non-stalked, linear or divided, 1.5-3.5 cm long, with entire edges. The uppermost leaves gradually change into 3-lobed bracts, supporting the flowers. Owl-clovers have small roots because they are annual plants which must start from seed each spring. Plants may parasitize the roots of other plants. The fruits are narrow capsules filled with tiny seeds. The capsules are symmetrical, egg-shaped, the seeds are 1.2-1.5 mm long.
Guide to Identify Presented Species of Genus Orthocarpus
FLOWERS IN DENSE, ELONGATED CLUSTERS
O. luteus Yellow Owl-clover Stems slender, 10-40 cm tall, glandular-hairy. Dry, open sites, plains-montane.
Flowers yellow, tubular, 9-14 mm long, wider near tip. Bracts are 3-5-lobed.
Leaves alternate, linear, 1.5-4 cm long, stalkless, rough-hairy.