Rawhide Hill Onion
(Allium tuolumnense )
Description: Rawhide Hill onion is perennial herb that grows from a bulb each spring. Its inflorescence is a spherical cluster of from 20 to 60 white flowers. The plant has only a single basal leaf that is round in cross section and 10 to 20 inches (25 to 60 cm) long. Leaf and stem are blue- green in color. The fruit has 6 crests on top (2 atop each of the three fruit lobes or carpels) and each of these crests has an irregular boundary. Onion aroma is evident when tissue is injured (to avoid unnecessary injury to plant, break off only the tip of the leaf to smell).
Distribution: Rawhide Hill onion is only known from Tuolumne County on the Red Hills serpentine body. Rawhide Hill, Red Hills and the Woods Creek drainage area are the primary centers of distribution. BLM has land in each of these areas that supports this species.
Habitat: Steep eroding serpentine slopes with sparse vegetation and little shrub or tree cover. Associates include buckbrush, foothill pine, California melic, squirreltail, Red Hills soaproot.
Flowering Period: March to May
Similar Plants: Other onions of the Sanborn's onion complex have a similar growth form with a single cylindrical leaf. Jepson's onion, (Allium jepsonii) which also grows in western Tuolumne County, has crests on the fruit that are smooth rather than irregular. The petals (tepals) of Jepson's onion are more pointed and vertical versus the petals of Rawhide Hill onion which are rounded and spreading. Jepson's onion is found on a volcanic substrate in Tuolumne County (but it is also found on serpentine in Butte County). Congdon's onion (Allium sanbornii var. congdonii) has stamens longer than the petals (tepals) and inner petals longer than outer (5/4 to 3/2 as long). Rawhide Hill onion has stamens and style shorter or equal to the petals, and all petals approximately equal. Congdon's onion and Rawhide Hill onion grow together in some areas, but Rawhide Hill onion blooms earlier in these situations.
Status: BLM Sensitive, California Native Plant Society List 1B
Field Office: Mother Lode