The browning grass of Potrero Meadow has a few bright splotches of color. The pale purple blossoms of one-leaf onion (Allium unifolium) are held a few feet high atop a fleshy, leafless stem; two or three linear leaves grow from the base (I’m not sure where the name “one-leaf” came from).
One-leaf onion is found in coastal counties from central California to southern Oregon. Look for it in moist clay or serpentine soils, especially along grassy streambanks.
Native onions, including this one, were an important food source for indigenous Californians. According to the Native American Ethnobotany Database, one-leaf onion bulbs were traded for other goods such as skins, baskets, or pottery. Bulbs were eaten raw, roasted, or fried, as well as used for seasoning (though I would want to do more research before eating it, since the Mendocino Indians considered it poisonous, and the California Poison Control database lists it as minorly toxic). 
Flowers Of Marin 