
San Franciscan Onion
Allium peninsulare var. franciscanum
NATIVE – CA ENDEMIC
Description (Jepson, PlantID.net)
- Monocotyledon
- Monocots are a major lineage of flowering plants; see family for general characteristics
- Onion Family (Alliaceae)
- Perennial herb
- Grows from a bulb (short underground stem with fleshy leaves, e.g. onion)
- Stem is a scape (leafless stem rising from ground level)
- Leaves
- 2-3 long, slender, and curved (≤ 2 ft.), growing from stem base (basal)
- Channeled, with deep longitudinal grooves, or cylindrical
- Usually wither before flowers open
- Flowers
- Inflorescence (flower arrangement) is an open umbel (a spoke-like flower cluster with stalks radiating from a single point) of 5-35 flowers at the end of a long, leafless stalk (scape)
- 2 fused bracts (modified leaves at base of inflorescence) become pale and papery with age
- Each magenta flower has 3 petals and 3 sepals (outer flower parts), in 2 separate whorls, similar in appearance and collectively called tepals
- Tepal tips are more-deeply colored, pointed, and recurved
- Ovary superior (above the attachment of other flower parts)
- Inflorescence (flower arrangement) is an open umbel (a spoke-like flower cluster with stalks radiating from a single point) of 5-35 flowers at the end of a long, leafless stalk (scape)
- Fruit is a capsule (a dry, multi-chambered fruit that splits open at maturity) with small black seeds
- Height to 18 in.
Distribution
- Native and endemic (limited) to California
- Grows in woodland, valley and foothill grasslands
- 50-54% of plants occur on ultramafic soils, e.g. serpentine; see ultramafic affinity rankings (Calfora per Safford and Miller 2020)
- See Calflora for statewide observations of this plant
- California Rare Plant Rank: 1B.2 (rare, threatened, or endangered in California and elsewhere)
- Grows at elevations to 1,000 ft.
Uses (San Mateo County Parks prohibits removal of any natural material)
- Wildlife
- Larval food source (host) for several moth species, e.g. alfalfa looper moth (Autographa californica)
- Pollinated by insects
- Native people (for Allium species)
- Ate the bulbs boiled, steamed, roasted, or baked in earthen ovens
- Ate fresh stems and leaves (Anderson 2005)
- Bulbs used as an analgesic for insect stings and bites
- Syrup from plant juice used to treat colds and sore throat
- See Onion/Garlic Family (Alliaceae) for more details about how Native people actively managed edible geophytes
Name Derivation
- Allium (AL-ee-um) – from the Latin for “garlic”
- peninsulare (pen-in-soo-LARE-ee) – referring to the species Allium peninsulare having been first collected in Baja California, a peninsula
- franciscanum (fran-cis-can-um) – referring to the San Francisco peninsula, where this variety primarily grows
Notes
- Geophytes (e.g. plants growing from bulbs, corms, rhizomes, or enlarged taproots) are well adapted to survive fire, our Mediterranean climate’s long, dry summers, and extended droughts
- Above-ground growth dies back after flowering, while underground the plant survives with stored water and nutrients
- Leaves have an oniony smell
- Variously placed in other monocot families in the past, including the Lily family (Liliaceae) and, currently, the Amaryllis family (Amaryllidaceae)
ID Tips
- May be confused with 2 other commonly-seen onions (Allium species) at Edgewood – pitted onion (A. lacunosum var. lacunosum) and the non-native three-cornered leek (A. triquetrum) – and with Ithuriel’s spear (Triteleia laxa) in the Brodiaea family
- Of these, only Franciscan onion has magenta petals with recurved tips

© KKorbholz (L), AFengler (LM), DSchiel (RM, R)
Pitted Onion | Three-cornered Leek | Franciscan Onion | Ithuriel’s Spear | |
Stem Height | ≤ 14 in. | ≤ 16 in. | ≤ 18 in. | ≤ 28 in. |
Pedicel Length¹ | ≤ 0.5 in. | ≤ 1 in. | ≤ 0.8 in. | ≤ 4 in. |
Flower Color | white or pale pink with dark midveins | white with green midveins | magenta with recurved petal tips | blue-purple with dark midveins |
Edgewood Habitat | serpentine outcrops | disturbed areas (i.e.main entrance) | north-facing woodlands | woodlands and grasslands |
At Edgewood
- Found in north to northwest facing woodlands
- No iNaturalist observations are documented because locations of rare species are obscured
- Flowers April – May
Specific references
Alexander, E.B. 2010, Oct. and 2011, Jan. Serpentine soils and why they limit plant survival and growth. Fremontia 38/39: 28-31.
Anderson, M.K. 2005. Tending the Wild. University of California, Berkeley.
Safford, H.D. and J.E.D. Miller. 2020. An updated database of serpentine endemism in the California flora. Madroño 67: 85-104. BioOne Complete.
Safford, H.D. 2010, Oct. and 2011, Jan. Serpentine endemism of the California flora. Fremontia 38/39: 32-39.