By Mark Gutglueck
Desert Senna is a perennial subshrub in the family Fabaceae, native to the Mojave Desert and Sonoran Desert in southeastern California, southern Nevada, and Arizona in the United States, and northern Baja California in Mexico. It is known by its scientific name, Senna covesii, as well as its alternative names, Coues’ senna, rattleweed, rattlebox, dais, or cove senna.
It is found on desert plains and in sandy washes between 1,500 and 1,900 feet above sea level, and is very common in Joshua Tree National Park. The use of the name Coues’ senna is an honorific for ornithologist Elliott Coues.
It grows to one foot to two feet tall, and is leafless most of the year. The stem is roughly the one to two foot height of the plant with leaves that are pinnate, one-and-a quarter inch to almost three inches long, with two or three pairs of non-terminal leaflets; the leaflets are elliptical, with stipules that are bristle-like, some persistant; with four to eight leaflets, overlapped, opposite and short-stalked. The oblong-obovate, prominently veined flowers are golden-yellow in color, with five rounded petals about half of an inch long. The flowers bloom from April to October and have an inflorescence featuring few flowered axillary raceme of one fifth to three-fifths of an inch. The oblong fruit is erect and dehiscent, four fifths of an inch to two inches from end to end. It puts out several seeds.
The senna covessi prefers full sun and is tolerant of many soil types as long as they are well-drained. It is very easy to establish and is often planted by landscapers and as part of roadside wildflower programs. Flowers are visited by carpenter bees and bumblebees. Sulphur butterflies use the plant as a larval food source.
Desert Senna is drought tolerant and works well in rock gardens and other dry areas.
Formerly known as Cassia covesii, it a leguminous bushy plant covered with dense white hairs.