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 phylogenetic 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 A-B are found on this wiki page.
Allium abramsii (Ownbey & Aase ex Traub) McNeal is a California species found in the higher foothills of the central Sierra Nevada. It has rose-purple flowers. Photo by Mary Sue Ittner
Allium acuminatum is native to the Western United States and Canada. It has bright rose to purple urn like flowers in open umbels and blooms May to July. It has sharply pointed tepals, the outer recurved and the inner with inrolled margins and is sometimes known as the Tapertip Onion. Another common name is Hooker's Onion. Photos 1-3 by Mary Sue Ittner. The last photo was taken by Richard Haard.
Allium amplectens is common in hot dry openings west of the Sierra Nevada in California and occasionally in Oregon and Washington. It is a variable species, with some plants forming small inflorescences, while others form much larger ones. Flowers range from white to pink in color. Not all forms of Allium amplectens are easy to grow. Photos 1-2 taken by Mark McDonough shows a pink form that is very easy to grow under normal garden conditions (eastern US), and produces a profusion of light pink starry blooms in May. Collections from arid regions are growable if planted in raised sand or clay beds. Photos 3-6 were taken by Nhu Nguyen of a form that needs a dry summer. Photo 3 show plants taken at the Tilden Botanic Garden. The last photo shows the texture of the bulb scale important in identification of many American alliums.
The first two photos were taken by Nhu Nguyen. The first is a habitat shot (Lake County, CA) showing this species growing near a stream bed. This form is able to grow on serpentine soil. The second shows a white form of this species which requires a dry summer dormancy. The last three photos by Mary Sue Ittner shows plants photographed in April 2005 at Pinnacles National Park and plants flowering in the Vina Plains Preserve in April 2006.
Allium amplectens 'Graceful' is an easily grown adaptable selection. Here are photos taken by Travis Owen showing plant in various stages of growth. The first photo shows the leaf bract towards the base, possibly a helpful characteristic to identifying the species.
Allium bolanderi S.Watson (syn. Allium stenanthum Drew) is a small onion growing in decayed granitic soil under native oak trees in California and Oregon. The bulbs are smooth, elongated, and less than 1/2" in length. Bulbs are connected to the plants by a delicate white rhizomes. It requires a very dry summer with absolutely no water. Photos are taken by Nhu Nguyen. The 1st photo shows a darker form of the species. The 2nd photo shows an in situ shot in Yolo County, CA, growing among poison oak.
The photos below were taken by Nhu Nguyen. The 3rd and 4th photos are closeup photos of the flowers and inflorescence. They also show the powdery quality of the underside of the tepals. Photo 4-5 shows the bulbs dividing from two to four bulbs. The last photo shows the bulb which lays in the ground horizontally just as pictured here. The remnants of the rhizome can be seen on top of the bulb.
Allium bolanderi var. mirabile (L.F.Hend.) McNeal (syn. Allium mirabile L.F.Hend., Allium roguense M.Peck) is a small white flowered variety native to Southern Oregon and Northern California. It bloomed in June in Rogue River, Oregon. Photos by Travis Owen.
Allium index - Allium flavum Relatives - American alliums A-B - American alliums C - American alliums D-F - American alliums G-H - American alliums I-M - American alliums N-R - American alliums S-Z - 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