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Description

Desert marigold is an annual or short-lived perennial with white-wooly leaves forming a dense mound about 6 to 8 inches (15-20 cm) in diameter. Flower heads perch well above the foliage on 1 foot long (30 cm) stems. The flat 1 inch (2.5 cm) daisies are bright yellow.

Range

Desert marigold grows mostly on bajadas and in valleys throughout the northern Sonoran, southern Mohave, and northern Chihuahuan deserts. It is one of the most common wildflowers, often abundant on disturbed soils such as road shoulders.

Notes

This is perhaps our most consistent showy roadside wildflower; it blooms in any season after a moderate rain. On hard soils such as caliche, desert marigold is replaced by the somewhat similar Bahia absinthifolia which has no vernacular name except its genus name). The foliage of bahia is more sparsely distributed; its stems arise from perennial underground rhizomes that form colonies. Bahia leaves are less woolly and the flowers slightly smaller than are those of desert marigold. Bahia's range extends into pine forests.

The sunflower family is stunningly successful. It is the largest plant family, or the second largest after orchids, depending on the criteria used, with over 20,000 species occupying almost all of the world's habitats except underwater. The genus Senecio (groundsel) alone has 1000 species. So many variations within a single group make composites the bane of many botanists seeking to identify the species. Because of this and the great preponderance of yellow flowers, unidentified plants are often semi- affectionately dubbed "DYCs"(damn yellow composites). This term has been adopted by some Mexican botanists as "PCAs"(pinchi compuestas amarillas). The family is well represented in the Sonoran Desert, constituting, for example, 16% of the Tucson Mountains' flora (105 species and subspecies).

The flowers, also called florets, are nearly always clustered into heads, with each subtended by a whorl or whorls of modified leaves called bracts (the involucre). There are two general forms of flowers. A disk flower, in its most complete form, has five petals fused into a tube, with a tube of five fused anthers inside the petal tube, and a two-lobed stigma exserted through the anther tube. A ray flower (a "petal" of a daisy) is similar, except that some of the fused petals extend on one side into a flat strap-like ligule. Flowers may be unisexual or sterile, lacking either or both "male" and "female" sexual parts. Each functionally "female" flower, whether ray or disk, has a single inferior ovary with a single ovule. If the ovule is fertilized, it will develop into a single seed in a special fruit called an achene. Each head may have only ray flowers or disk flowers, or both.