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Species Spotlight: The Yucaipa Onion is a Rare Botanical Gem

Mar 20, 2024 | MSHCP, Species

Hidden among the picturesque landscape of western Riverside County, you may find a botanical gem known as the Yucaipa onion (Allium marvinii). Designated as a Western Riverside County Multiple Species Habitat Conservation Plan narrow endemic plant species and recognized as rare by the California Native Plant Society, the survival of this elusive species is dependent on the clay openings within chaparral habitat.

The Yucaipa onion was originally described by J. Marvin in 1921 who labeled his collection ambiguously as discovered in “Banning.” It wasn’t until several years later that this species was rediscovered northeast of Yucaipa, earning the moniker of “Yucaipa onion.”

Belonging to the genus Allium within the Liliaceae (Lily) family, this clay-loving rare plant species emerges seasonally from an underground bulb. Its slender stem and crown of flowers stand tall – gracing the landscape with a modest white perianth measuring a mere 5 mm in length. Each delicate white petal is marked with a brown stripe that gradually fades to a lavender hue. Each flower’s ovary features distinctive wing-like crests, although no literature has ever been published on this species’ genetic makeup.

The Yucaipa onion’s growing season spans anywhere from three to eleven months and tends to bloom between April and May. However, during dry years, the resilient Yucaipa onion may not flower – contributing to the difficulty in locating this species. The MSHCP has identified at least 1,200 acres of land supporting suitable habitat within the San Bernardino Mountains bioregion for conservation in western Riverside County to preserve the elusive species.