On these pages photos of North American Allium species will be featured. There are approximately 130 taxa in North America, almost half of which occur in California as the center of diversity. Besides a few species that are widely grown, namely Allium cernuum (nodding onion), the Californian A. unifolium (popularized by the Dutch bulb trade) and the lesser known A. stellatum (prairie onion), the North American onion species have been largely ignored by the horticultural world. There are also about 15 species native to Mexico, similarly rare or absent from horticulture. Eastern American species generally need a cool - cold winter dormancy period with some to lots of rain. Western American species, especially those in the Pacific States follow a Mediterranean pattern where they need a moderately cold wet winter and a cool dry summer.
Taxonomically, there have been few changes in American species. A recent phylogentic study by Nguyen et al., 2008 found that North American alliums are distinct from European species and those occurring in the 
California Floristic Province (CFP) are distinct from eastern American species. California holds a wide variety of species whose forms are distinctive in leaf morphology. Species related to Allium falcifolium form falcate leaves whereas species related to Allium jepsonii form a single leaf from which the inflorescence emerges on the side. Many CFP species have also adapted to a special type of soil called serpentine which is very high in minerals such as magnesium, making it toxic to many plants. Some Allium species are so adapted that they can only be found on serpentine soil in the wild.
American alliums from S-Z are found on this wiki page. American alliums A-C – American alliums D-H – American alliums I-M – American alliums N-R
Allium sanbornii is a large onion restricted to the Sierra Nevada and southern Cascade foothills of California. It is only found on serpentine outcrops. Photos by Nhu Nguyen. Seeds sprout readily and is actually one of the easier California onions to grow, given that one has access to serpentine soil. It blooms quite late in the season around July where most other plants have already gone into dormancy. It requires a very dry summer dormancy period.
Allium serra is an from the central coast ranges of California, found in grassy slopes, often under oak trees, blooming from March to May. It has pink flowers which become more papery as they age. The first photo is by Mary Sue Ittner, and the second by Kristina Van Wert from the Mendocino Coast Botanical Gardens collection. The next 4 photos are taken by Nhu Nguyen showing the flowers, flowers going into seeds, a habitat shot, and the beautiful "herring bone" pattern on the bulbs. This character is very important to identifying this and several other related species.
Photo by Mary Sue Ittner of a flower blooming April 2005 in Bear Valley in Colusa County, California.
Allium sharsmithiae is a small onion restricted to the Mt. Hamilton Range in central California. It occurs only on serpentine soil and needs a very dry summer dormancy. The leaves will often die down before the flowers bloom. Photos by Nhu Nguyen taken in habitat.
Allium shevockii is also another small but beautiful onion with a rather large inflorescence of dark red, petals. It is a relatively recent discovery, found only in Kern County, California where it grows on metamorphic outcrops or talus. It was first collected by Jim Shevock, for whom the species was named. Photos by Nhu Nguyen.
Allium texanum - a species from... you guessed it, Texas. First described and published in 1990 by Thad Howard, one of several species emerging from the overgeneralized muddle of Marion Ownbey's Allium canadense var. fraseri. Hardy here in New England, with gray twisting foliage, and attractive white flowers in late June through July. Photo by Mark McDonough.
Allium tolmiei at the Lawrence Grassland Preserve (Nature Conservancy) near Shaniko, central Oregon, flowering in mid-May. This small onion grows in so-called biscuit scabland, a type of terrain featuring raised mounds of soil surrounded by "moats" of small to medium-sized rocks, and patches of similar rock. It grows only in the rocky spots, surrounded by sagebrush scrub in the deeper soils. Photo by Jane McGary
Allium unifolium is a California species found in moist grasslands in spring. It is one of the most commonly grown Californian species as a landscape bulb and multiplies rapidly. Seeds are very viable and they spread throughout botanical gardens where they are planted. The bulbs are connected to the plant by a thin rhizome. The first two pictures taken by Bob Rutemoeller show it in habitat on the Sonoma coast and a close-up too. The third is from Kristina Van Wert and the Mendocino Coast Botanical Gardens collection. The last two are taken by Nhu Nguyen.
Allium index – American alliums A-C – American alliums D-H – American alliums I-M – American alliums N-R
Allium flavum Relatives – Allium hybrids – Big Ball alliums – Blue alliums – chives – Domed alliums – Drumstick alliums – Miscellaneous alliums A-E – Miscellaneous alliums F-M – Miscellaneous alliums N-R – Miscellaneous alliums S-Z – Rhizomatous alliums
Return to the PBS wiki Photographs And Information page