The genus Allium (TOW)
Sun, 02 Mar 2003 21:14:16 PST
Introducing the PBS topic of the week:  Allium

The genus Allium represents a very large and complex group found throughout 
the Northern hemisphere, with only one or two species found in the southern 
hemisphere, although those are believed to have been introduced.  The species 
count varies tremendously from 500 to 1000.  A very recent scholarly work; 
"Nomenclature Alliorum - Allium names and synonyms - a world guide", Kew, 
1998, compiled by 5 top taxonomists dealing with the genus Allium, enumerates 
all known Allium species and synonym epithets.  Hand counting the taxa on 
which the 5 authors generally agree with species/subspecies status, I count 
857 taxa (769 species + 88 subspecies).

Once part of Liliaceae family, the genus is now the 'type' for the family 
"Alliaceae", which includes such genera as Ipheion, Nothoscordum, 
Nectaroscordum, Caloscordum, Tulbaghia, and a few others.  Until recently, 
the North American genera Triteleia, Brodiaea, and Dichelostemma were 
considered part of the Alliaceae, but were moved into their own family 
Themidaceae.  And of course, the genus Allium is best known for the handful 
of species which compose the world food crops; onions, leeks, garlic, 
scallions, and chives.

Allium species can be lumped into two types, those that have true bulbs, and 
those that grow from rhizomes with less-developed vestigial bulbs attached to 
them.  The bulbous alliums tend to grow and flower early, then go completely 
dormant afterwards.  The "rhizomatous" alliums tend to be season-long growers 
and flower much later in summer.  There are many exceptions to these 
gerenalizations.  Consistent with many large genera, the genus Allium is 
subdivided into sections and subsections that help organize the species into 
groups of similar species.

What I like about Alliums
1.  With the great diversity of species, it is possible to have Alliums in 
flower from early spring (March) to late autumn (or even early winter if the 
climate is mild enough).  When most hardy bulbs have long since finished 
blooming, the alliums carry on strong through the summer and fall months.

2.  The flowers are nectariferous and sweet smelling in many (most) species, 
attracting swarms of bees, butterflies, and wasps.

3.  Growth pattern, dormancy cycles, and general landscape effect can vary 
dramatically, offering considerable garden appeal and potential.

4.  The genus has hardly been touched by the hybridization craze, and is a 
plum ripe for the picking.

5.  There are so many species to whet the appetite, one could never grow them 
all in a lifetime.

6.  In spite of a reputation for being weeds, garnered from a few bad apples 
(or bad onions) in the genus, such as the horrible crow garlic or A. vineale, 
 most are really delightful plants of subtle and irresistable beauty.

There's very little commercially available literature for gardeners 
interested in learning about the genus.  The only popular book that deals 
with Allium is "Alliums, the Ornamental Onions" by Dilys Davies published in 
1992 (now out of print) .  It's a good "starter" book to learn about alliums. 
 General bulb books, like Roger Phillips and Martyn Rix's formidable 
photographic guide; "The Random House book of Bulbs", covers a mere sampling 
of species given the breadth of species available.  One must search out 
scholarly floras, thesis studies, and other scientific publications, to gain 
an understanding of the genus.  The world awaits a comprehensive treatise on 
the genus.  If only Brian Mathew would consider taking on such an epic work, 
given his exemplary work "A review of Allium section Allium", 1996,  covering 
115 species; I'm convinced that he has what it takes to tackle this behemoth 
of a genus.

North American alliums
This is a group that is little known, aside from a couple of easy to grow and 
well-known species; namely Allium cernuum (nodding onion) and A. unifolium 
(mass propagated by Dutch bulb growers).  There are many terrific North 
American species to try (about 135 taxa). including about 15 Mexican species 
which are virtually unknown in cultivation and literature.  The first 
complete enumeration and discussion of North American species appears in a 
Timber Press book (sponsored by the North American Rock Garden Society)  
entitled "Bulbs of North America".  I co-authored the section on Allium with 
Jim and Georgie Robinett (edited by Jane McGary).  To read about or purchase 
this book, go to:…

Some favorite alliums
A brief smattering of favorite alliums, although I'm leaving out many.  Try 
them, and you'll get hooked too.

Allium beesianum - one of the many lovely rhizomatous Chinese species, 
appreciating some shade and good humusy soil.  Mixed up in cultivation and 
rarely available true-to-name, this is a very beautiful and refined species 
that begins flowering late August, continuing into September and October.

Allium cernuum - the American "nodding onion" is commonplace, yet beautiful.  
Less known is that it's incredibly variable, from dwarf forms under 6" (15 
cm) to tall forms over 2' (60 cm), with flower color from white to deep 
rose-purple, and found in a whole range of inflorescence, leaf, and plant 

Allium cuthbertii - a rarely encountered, slow-growing species from 
southeastern USA.  It's a refined beauty, flowering in late June with upright 
domes of white and pink striped flowers.

Allium flavum - European species with informal fireworks sprays of little 
yellow bells.  Variable, from dwarf forms under 15 cm to tall forms 18-24 cm 
tall.  Blooms June-July.  LIkes full sun, and prospers in dry soils.  Forms 
with nearly silver-blue glaucous foliage and stems are the most attractive.

A. flavum ssp. tauricum - a variant with yellow flowers varaiably tinged with 
pink, brownish, or other tones.  Via selection over the years, a fantastic 
array of colors has arisen in my garden, from pure pinks, to mauve, white, 
lime green, tan and beige shades, orange,  pinky-orange pastels, deep burnt 
red and brown-red shades, to name but a few.  Most grow only 6-8" tall (15-20 
cm).  They're a delight in early July.

A. guttatum ssp. sardoum - this fine European species has many close allies, 
and is a good representative of the so-called "drumstick onions"; those that 
have fine slender stems and a tight knobs of bloom.  In this species the 
flowers are white and the tepals marked with a dark greenish spot.  Grows to 
about 60 cm.

A. karataviense - this species is one of many section Melanocrommyum onions, 
the ball-shaped onions from the high dry mountains of central Asia.  The 
foliage is gorgeous, being very broad, rounded, pleated, and purple stained, 
like the finest tulip leaf, with large dense globes nested right ontop of the 
foliage.  There are several named clones available.  Most "Melanocrommyum" 
onions are tall giants, such as the famous Allium giganteum.

A. mannii - a Mexican species that has proved to be perfectly hardy in the 
garden.  Slow growing, with handsome open clusters of white flowers in July, 
on 16" (40 cm) stems.  It comes closest to A. plummerae, having central 
ovaries that age to a brownish orange color.

A. nutans - from Siberia and other Asian locales, a large and wonderful 
rhizomatous allium with heavy broad strap-like gray foliage, and dense poms 
of starry blooms in mid to late summer, the buds initally drooping or 
nodding, thus the species name.

A. perdulce - an American species from the central and southern prairie 
states.  One of the very best and most delicious.  Flowers in spring, on 4-6" 
stems (10-15 cm) with rich pink urn-shaped flowers that have an intense 
hyacinth-like fragrance.  Extremely slow to increase and recalcitrant in 

A. plummerae - a wonderful American species that's hardly known, but should 
become popular.  From southwestern USA mountains, growing at high elevation 
in most soils, it's a terrific species to grow in good moist garden soil in 
full sun, making upright tufts of glaucous foliage and upright clusters of 
ample, star-shaped white flowers and tan to brownish-orange ovaries.

A. rotundum - another of the drumstick onions, this one flowers in high 
summer with tight oblong knobs of deep red-purple, at times appearing nearly 
black-purple, wafting atop 18"-30" stems (45-75 cm).  It's like a smaller, 
darker, more refined A. sphaerocephalon.

A. schoenoprasum (chives).  An incredibly polymorphic species, found 
throughout the northern hemisphere, and is the only species found in both 
Europe/Asia, and in North America.  The familiar chives is much more variable 
than people realize, from dwarf forms only 6" (15 cm) tall, to much larger 
plants, with flowers ranging from pure white, through all shades of mauve, 
lavender, pink, rose and purple.

A. senescens - A very common rhizomatous species that makes nice clumps of 
summer foliage.  The European form with glossy strap-shaped green leaves 
known as A. senescens ssp. montanum, has been taxonomicaly revised and is now 
named to Allium lusitanicum.  The type species A. senescens now refers to the 
Asian form with gray or glaucous foliage.  These plants have dense lollipop 
spheres of mauve, pink, or rose flowers in mid summer to autumn.

A. sibthorpianum - a very dwarf Turkish species that flowers in June.  It is 
allied to Allium flavum, and crosses with A. flavum ssp. tauricum.  It only 
grows 7-10 cm tall, and has charming clusters of pearly pink bells that age 
raspberry rose.

A. stellatum - a tall American species from the Great Plains (central USA) 
but with a broad distribution from Canada to Mexico, it's extremely variable. 
 I grow summer blooming forms from Canada that flower in July and August, but 
there are also late forms with rich rose-pink flowers that flower in 
August-September-October.  Interestingly, this species spontaneously crosses 
with European rhizomatous alliums in the garden, producing some weird and 
wonderful hybrids.  It is closely allied to Allium cernuum.

A. togasii (alt. spelling Allium togashii) - a wonderful Japanese species, 
with fine grassy tufts of foliage in spring and early summer, then multitudes 
of spherical pinkish globes on short 4"-6" (10-15 cm) stems in August to 
September.  There is a taller form that grows to 16" (40 cm) and flowers in 

I have posted a good number of photos to the PBS wiki allium page at:…

More photos will be added during the week!

What alliums do you grow???

Links to more allium photos and sources:

Mark McDonough        Pepperell, Massachusetts, United States    "New England"               USDA Zone 5
>> web site under construction - <<
     alliums, bulbs, penstemons, hardy hibiscus, western 
            american alpines, iris, plants of all types!

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