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 A-C are found on this wiki page. American alliums D-H – American alliums I-M – American alliums N-R – American alliums S-Z
Allium abramsii 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 amplectens is a variable species, some of which form small inflorescences, while others form much larger ones. They range from white to pink in color. Not all forms of Allium amplectens are easy to grow, probably due to their preference for arid desert habitat. This particular form is very easy to grow under normal garden conditions, 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. The first two photos were taken by Mark McDonough, the 3rd by Kristina Van Wert from the Mendocino Coast Botanical Gardens collection, and the 4-6th by Nhu Nguyen, and the last by Mary Sue Ittner. The 4th photo is a habitat shot (Lake County, CA) growing near a stream bed. This form is able to grow on serpentine soil. The 5th photo is the texture of the bulb scale important in identification of many American alliums. The 6th photo shows a white form of this species which require a dry summer dormancy. The last photo shows a white form photographed in April 2005 at the Pinnacles National Monument.
Allium bolanderi 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 3rd and 4th photos are closeup photos of the flowers and inflorescence. They also show the powdery quality of the underside of the tepals. The 5th 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 campanulatum - an odd species, but one that I like nonetheless. It flowers in early spring, preferring clay soil in a raised bed, in full sun. The flowers are nearly at ground level and typically show a two-toned flower, the center of each flower being pale compared to the deeper ends of the tepals. The stems are very brittle and easily broken. The flowers are different from other American alliums in that they open completely where the tepals lay on a flat plane. They are found in California, Nevada, Oregon and Washington states. First photo by Mark McDonough, second photo by Nhu Nguyen.
Allium canadense "red bulbil form from Texas" - Typical Allium canadense is best avoided as a weed because most of the flowers are replaced by bulbils, and aside from being ugly, the bulbils drop off and start new plants. Over the years I've kept just this one form with its white red-tipped bulbils, occasionally sputtering forth a white bloom or two. With the green sprouting tips to the bulbils, I thought the plant had a whimsical appearance and was thus appealing. Each year I would cut the stems off, then bag and discard the promiscuous propagules. Now I wish I had kept a few, because last summer a wild animal dug up and ate the clump! (there are foxes in the yard, and they've taken to digging and eating some alliums, particularly A. paniculatum). Photo by Mark McDonough.
Allium canadense forma florosum - This is a rare non-bulbilliferous form of the weedy A. canadense, the type species being weedy on account of the many bulbils that replace the flowers. The plants shown here were collected by Thad Howard in Texas, found in a couple locations growing amongst millions of the normal weedy types. This name, proposed by Thad Howard, has not yet been published, yet this is a highly ornamental form with large heads of white to barely tinged pinkish flowers, and rarely 1-3 obscure bulbils. In the second "garden view" of the same plant, you can see what a fine statement it makes in the garden, growing to about 30" (75 cm) tall, flowering in June. Photos by Mark McDonough.
Allium cernuum - mass planting. In the first view, we see prolific blooms on a tall rose purple form of the "nodding onion" flowering in late June. The nodding onion hails from most states within the USA (and up to Canada) and therefore is extremely variable. In the lower left corner of the photo is Lilium formosanum var. pricei. In the second we see 4 nodding buds. It is clear why the "nodding onion" received such a common name, when one views the drooping buds. In this view the buds are just breaking through the bud spathe. The third is a similar view to the preceding, but here the flowers are open, showing nice pink rotund florets, hanging downwards. The final shot is a "good pink form" - the tall stems growing up through the invasive Campanula takesimana. Photos by Mark McDonough.
Allium cernuum 'Leo' - one of my favorite cultivars, with tall, stiff stems to 30" (75 cm) or more, topped with clusters of white flowers (sometimes showing a tinge of pink in cool weather) that are denser than normal. Also distinctive in it's late flowering, in full bloom in mid August. The foliage is also shorter and neater than most cernuum forms... could have some A. stellatum blood in it. In the last two close-up views of the flowers the very short and tight "crook-necked" buds, the later than normal flowering period, along with the sideways disposition of the inflorescence, indicates some A. stellatum influence. Photos by Mark McDonough.
Allium cernuum 'Oxy White' (syn. A. oxyphilum) - I've tried photographing this delicate beauty for years but never really captured the essence of this fine plant. From southeastern USA, once regarded as a separate species (A. oxyphilum), most authorities now regard this as merely a form of A. cernuum , as do I. It's a most airy and delicate plant, with slender stems, and thread-thin pedicels holding little white flower droplets. In the last photo, seedlings of A. cernuum 'Oxy White' show lots of variation and a tendency back towards normal cernuum appearance. Photos by Mark McDonough.
Allium cratericola - This is a lovely little onion restricted to California. It is most often observed in the wild in the Table Mountains in Butte County. The inflorescence stays appressed to the ground. In California, it tends to bloom much earlier than other onions, often times forming seeds by the middle of April. It can tolerate a variety of substrates including serpentine, volcanic, and granitic sediments. The key to cultivation is that the medium must be well drained and containing little organic matter. It likes being in full sun. Winter water is necessary, but a dry summer dormancy is extremely important. Photos by Nhu Nguyen.
Allium crispum is a species that grows in the coast ranges of California south of San Francisco in clay and serpentine soils. This is a long blooming Allium. The first one was taken in 2004 showing flowering plants she is growing. The next three photos below are of plants growing in the wild. The first a flower in bud in Pinnacles National Monument and the next two are of flowers blooming along a bank on Jolon Road in Monterey County. The last picture shows it with a light colored Collinsia heterophylla. First 4 photos by Mary Sue Ittner. The last photo by Nhu Nguyen shows the crinkled edges of the petals, thus giving this species it's specific ephithet.
Allium index – American alliums D-H – American alliums I-M – American alliums N-R – American alliums S-Z
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
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