Allium falcifolium occurs on serpentine soils and outcrops from San Francisco Bay to Oregon. It is often found on slopes with excellent drainage. It is also never found too far away from oak trees, relying on the organic matter from decaying oak leaves. The hummus contents can range from 50% - 20% in the wild. There are two flower forms of this species, with the more common magenta pictured below and a more rare and often elusive white form. 1st photo by Jane McGary, 2nd by Mary Sue Ittner, and the last a macro of a specimen grown by Nhu Nguyen.
Habitat photos from Nhu Nguyen are shown below. Photos 1-2 shows the habitat in Napa County where they flower with Eschscholzia caespitosa amongst the serpentine rocks. Photo 5 illustrates the sickle shaped leaves.