El Rosario Goldenbush

Hazardia rosarica is a shrub characterized by its lemony fragrance, glabrous zigzagged branches, toothed glutinous leaves, and yellow flower heads that only contain disc flowers. It is most similar to the polytypic Hazardia squarrosa, whose southern subspecies grindelioides approaches the range of H. rosarica, and both species share a lack of ray flowers. However, H. squarrosa is a much taller, larger shrub with a characteristic pubescence on its stems and a different fragrance, as opposed to H. rosarica with its smaller stature, completely hairless stems and sweet, lemony fragrance.

Morphology. Hazardia rosarica is a glutinous, fragrant shrub 2–9 dm (7.9–35.4 in) tall, with many erect to ascending branches emerging from a woody base. The branchlets are zigzag, and in youth are very tan and measure 1 mm (0.039 in) in diameter but become gray and measure up to 3 mm (0.12 in) thick in age. The internodes average around 5–15 mm (0.20–0.59 in), and the branchlets are glabrous and have glutinous to granular surfaces. The leaves range from sessile to subpetiolate, rarely with auriculate-clasping or subclasping bases, and are shaped obovate to spatulate with obtuse to rounded-acute tips. The leaves measure 10–25 mm (0.39–0.98 in) long by 5–12 mm (0.20–0.47 in) and 1–2 mm (0.039–0.079 in) wide at the base. …

Hazardia rosarica is endemic to Mexico, and is only found in the state of Baja California. It occurs along the coastal foothills from northeast of El Socorro to the southeast of the town of El Rosario, usually within 8 km (5.0 mi) to 12 mi (19 km) of the coast. Hazardia rosarica is typically found at 75 m (246 ft) to 475 m (1,558 ft) in elevation on north and east facing slopes and ridgetops, and it usually grows in association with Agave shawii, Rosa minutifolia, Euphorbia misera, and Ambrosia chenopodiifolia. Other associates include Aesculus, Dudleya, and Bergerocactus, and Hazardia vernicosa. Although endemic to a small area, it is typically locally abundant where it is found.

In the protologue, Moran reported that most natives of El Rosario did not have a name for the plant, but that one man said the plant was used in a remedy for toothache.