Artificial Simplified Key to the Blue Alliums - with abbreviated species
descriptions |
The blue alliums do not represent a true taxonomic
"alliance", rather they are a collection of separate species and small
"subgroups" that simply share the common attribute of having blue flowers.
The following "artificial simplified key" was put together as an
identification aid for plants in cultivation. The species descriptions are
simplified, omitting most of the technical jargon that makes botanical descriptions hard
to visualize. To ease the task of identifying plants, the key was specifically
designed to use obvious leaf and flower characteristics only, thus avoiding bulb coat
diagnostics (which can change during the season and requires digging up the plant) as well
as avoiding minute floral characteristics that require a hand lens. If you have a blue
allium in flower, it should be possible to use a full flowering stem and a leaf or two,
with which to make an identification. |
| 1a |
Leaves hollow (fistulose) - |
leaves round in cross-section (terete), sometimes channeled
(canaliculate), to rarely 3-sided (trigonous), leaves sheathing the bottom 1/4 - 1/2 (or
more) of the flower stem. |
| |
2a |
Stamen filaments with broadened bases, usually with short tooth
(cusp) on each side |
|
3a |
Leaves 3-sided to channeled, inner stamen filaments toothless or
with 2 small teeth below middle. |
| |
Allium caeruleum
- bulbs rounded, with papery gray bulb coats, smooth and nerveless; stem 25-85 cm
(typically 45-60 cm), sheathed for 1/3 the height with 2-4 leaves; leaves hollow, 3-sided,
channeled, smooth or scabrous (rough) along the margins, 2-4 mm wide, shorter than the
stem; spathe persistent; umbel nearly spherical, many-flowered, open, often with a few
tiny bulbils; pedicels nearly equal and much longer than the flowers; flowers small,
starry, tepals cornflower blue with darker nerve, 4-5 mm long; stamens about as long as
the flowers, style exserted. Flowers June - July.
This
species is commonly available in autumn bulb bins and in bulb catalogs. It is a
tallish, slender looking plant that makes a nice splash of deep blue color in the early
summer garden. Tends to be short-lived, flowering less in subsequent years, needing
to be replaced with fresh bulb plantings. Often produces amusing anomalous flowers, with
one tepal or stamen transformed into a pedicel and sprouting another flower from within a
flower. |
| 3b |
Leaves semi-cylindrical, channeled, inner filaments with long
lateral cusps as long or longer than filament |
| |
4a |
Plants generally small (11-22 cm), anthers pointed (mucronate) |
| |
Allium caesioides
- bulbs rounded, papery gray bulb coats; one to rarely two stems per bulb, stems 11-22 cm
(rarely taller to 35 cm) sheathed for 1/3 - 1/2 the height with 2-3 leaves; leaves hollow,
1-2 mm wide; spathe persistent; umbel hemispherical to spherical, dense, many-flowered,
pedicels about 1.5 cm long, tepals purple-violet or becoming sky blue, with dark blue
midveins, 5-6.5 mm long, stamens about 2/3 as long as tepals.
According
to the type publication, Botaniska Notiser, 1969, Vol.122, pp.29-31, A. caesioides comes
closest to A. caesium. But A. caesium has a narrower bell-shaped flower, of a more bluish
color, tepals have a thicker consistency, and the stamen filaments are longer, with better
developed lateral teeth to the inner filaments. A. caesioides has less rigid leaves
with indistinct longitudinal ribs, pointed anthers, and grows at higher elevations. Grows
in the shade of taller plants. |
| 4b |
Plants generally taller (30 - 60 cm) |
| |
5a |
Flowers azure blue, light blue, grayish blue, or rarely white,
tepals 4-6 mm |
| |
Allium
caesium - bulbs rounded, bulb coats slightly leathery, gray, with
faint parallel nerves; stem 15-65 cm (usually on the taller range) sheathed for 1/4 - 1/2
the height with 2-3 scabrous (rarely smooth) leaves; leaves hollow, nearly round in
cross-section, about equal to stem height; spathe short, persistent; umbel dense,
many-flowered, rarely with bulbils, pedicels equal, 2-5 times length of tepals, tepals
narroly bell-shaped, azure blue to light blue (rarely white), with dark blue midveins,
stamens 3/4x or equal length of tepals, style slightly exserted. Flowers May - June
(July).
This
is a beautiful species, and evidently rather variable. The plants I've grown (see
photos) are rather tall at about 24" (60 cm), with large showy heads of pure light
sky blue with navy blue midveins. I believe there are some dwarf, darker
blue-flowered forms in cultivation, although I have not grown these. Allium caesium
is sometimes confused with A. cearuleum, and reportedly these species hybridize where
their distribution overlaps. Both are slender upright plants, but A. caesium is
easily distinguished once you've seen both. Allium caesium tends to have denser,
more upright, semi-fastigiate shaped flower heads, versus the the open globe-shaped head
of caeruleum, and caesium has longer, narrow-campanulate florets versus the smaller, more
open, starry florets of caeruleum. |
| 5b |
Flowers dark blue with distinct violet tinge, flowers narrower and
longer, tepals 6 mm |
| |
Allium
litvinovii - description similar to A. caesium, except stems are
slender, the flowers are usually darker with a distinct violet tinge, to a deeper violet,
the flowers commonly narrow and longer, narrowly cup-shaped, mostly 6 mm long, with deep
violet color midveins, style not exserted. Per the Flora of the USSR, white-flowered
plants are also known, found in "considerable numbers" in the Fergana Range. |
2b |
Stamen filaments, inner
ones with long lateral cusps on each side, as long or longer than stamen filament. |
|
6a |
Leaves sheathing lower 1/2 or more of the flower stems |
| |
7a |
Plants tall (40-70 cm), tepals long, 7-9 mm, flowers openly cone
shaped (campanulate-conical) |
| |
Allium aucheri
- bulbs rounded, bulb coats slightly leathery, grayish-brown, splitting lengthwise; stems
40-70 cm sheathed for 1/2 the height with 2-4 leaves, stem smooth and wiry; leaves hollow,
1.5-4 mm wide, smooth; spathe 2 segments, persistent; umbel spherical to
shuttlecock-shaped (oblong), dense, many-flowered, pedicels 3-6 mm long; tepals violet
blue to deep blue, with darker midvein, 7-9 mm long, openly conical shaped; stamens and
style shorter than the tepals. Flowers June - July.
From
high elevations (hardiness) and from seasonally moist mountain meadows, this choice
species should prove amenable to cultivation compared to allied species from lower
elavation desert locations (hierochuntinum, scabriflorum, and vuralii). It is said
to be distinct from the closely allium A. hierochuntinum because the short leaves of A.
aucheri develop in spring rather than the autumn as in other species. A tall,
slender species. |
| 7b |
Plants dwarf (5-20 cm), stems flexuous, tepals 4-5 mm, flowers
bell-shapped (campanulate) |
| |
Allium sannineum
- bulbs rounded, bulb coats reticulate-fibrous; stems 10-20 cm sheathed for 1/2 - 2/3 the
height with 2-3 leaves, stems semi-reclining, veined; leaves hollow, rounded in
cross-section, slightly taller than stem, 1-2 mm wide; spathe 2 segments,short,
persistent; umbel hemispherical to spherical, pedicels 5 mm long (possibly longer),
flowers bell-shaped, blue to blue-violet, 4-5 mm long; stamens, anthers, and style are
exserted. Flowers June - August.
A
dwarf, alpine species. Judging from the excellent drawing in Israel Journal of
Botany, Vol. 26, No. 3, 1977, page 136, this is a highly desirable species suitable for
the rock garden, if only it were available. |
| 6b |
Leaves sheathing lower 1/4 - 1/3 of the flower stems |
| |
8a |
Tepals 6-8 mm long, stamens and style included (not exserted) |
| |
Allium hierochuntinum
- bulbs rounded, bulb coats are brown, fibrous reticulated; stem 12-35 cm tall sheathed
for 1/4 - 1/3 the height with 2-4 leaves, stem smooth, wiry, slender; leaves hollow,
thread-thin, 0.5-1.5 mm wide, round in cross-section, smooth; spathe 2 segments,
persistent; umbel spherical, dense, pedicels 4-10 mm long, flowers narrow pinched-bell
shaped, violet blue, 6-8 mm long, papillose (dimpled) and scabrid; stamens and style
shorter than the tepals. Flowers March - May.
From
arid desert steppe, from low to moderate elevation, this species is likely to be difficult
and not hardy in my USDA Zone 5 garden. However, seed of this small, slender,
upright species is available from Monocot Nursery, England. Probably best for a bulb
frame or alpine house. Very closely allied to A. scrabiflorum. |
| 8b |
Tepals 4-5 mm long, stamens and style equal to tepals or exserted |
| |
9a |
Filaments exserted, leaves 1-1.5 mm & shorter to rarely = stems,
anthers purple or yellow |
| |
Allium
scabriflorum - bulbs rounded, bulb coats golden brown,
fibrous reticulated, forming clumps; stem 10-30 cm tall sheathed for 1/4 - 1/3 the height
with 2-3 leaves, stem smooth, slim, and wiry; leaves hollow, roundish in cross-section and
shallowly channeled, shorter to equally stem, thread-thin, 1-1.5 mm wide, smooth or
slightly scabrid; spathe 1-2 (or more) segments, persistent; umbel oblong to spherical,
dense, pedicels 3-10 mm long, flowers narrow pinch-bell shaped, violet blue with green
midvein or deep purple fading bluish (rarely whitish with green midvein), 4-5 mm long,
papillose and scabrid; stamens and anthers exserted, style shorter than tepals to slightly
exserted, anthers purple to occasionally yellow. Flowers June - July.
Very
similar to A. hierochuntinum, but has smaller flowers and exserted stamens. |
| 9b |
Filaments ~ equal tepals, leaves 1.5-2 mm, as long or longer than
stems, anthers white |
| |
Allium
vuralii - bulbs rounded, fibrous reticulated bulb coats; stem
to 30 cm tall sheathed 1/4 - 1/3 the height with 2 leaves; leaves hollow, thread-thin,
1.5-2 mm wide, as tall or taller than the stems; spathe 2 segment; umbel spherical, dense,
many flowered, pedicels about 1 cm long, flowers narrow urn-shaped, 5 mm long, pale bluish
violet with green midvein, outer tepals papillose on the midvein; stamen filaments
slightly shorter than to slightly longer than the tepals, anthers creamy-white.
Flowers July.
Known
only from the "type collection", thus somewhat obscure. |
| 1b |
Leaves solid |
leaves typically flat, in 1 species roundish in cross section
(semiterete) but not hollow, sometimes channeled, or with a keel on the underside, leaves
basal in all but 1 species. |
| |
10a |
Leaves basal (not sheathing the flower stems, or only sheathing
lower-most base of stem) |
|
11a |
Leaves semi-cylindical in cross-section (semiterete) |
| |
Allium cyaneum
- bulbs appear as narrow, thickened stem-bases, cylindrical, 0.2-0.6 cm thick, bulb coats
dark brown, clustered closely together, attached to rhizome; stems 10-30 cm (rarely to 45
cm); leaves 2-4, basal, solid, roundish in cross-section to channeled, thread-like,
1.5-2.5 mm; spathe 1-2 segments, early shedding; umbel irregularly semi-hemispherical, few
to moderate flowered, pedicels 1-2 times as long as tepals, flowers deep cobalt blue to
light blue or violet blue, openly bell-shaped, starry, tepals 4-6.5 mm long x 2-3 mm wide,
stamens long exserted to 2x length of tepals, style exserted. Flowers August -
October.
This
species is highly variable, with numerous forms in cultivation. It's small size,
neat cump-forming habit, little fountains of thready bright green foliage, and late
flowering, make this a valuable addition to the rock garden. Normally seen are
upright forms that reach 20-30 cm, occasionally they are much smaller plants with a
spreading growth habit. The small starry flowers with long exserted stamens make
this species unmistakable. |
| 11b |
Leaves flat, sometimes with an underside rib (keel) |
| |
12a |
Stamens included (not exserted) |
| |
13a |
Flowers large, 11-17 mm, margin of tepals are smooth |
| |
Allium
beesianum - bulbs appear as narrow, thickened stem-bases, cylindrical,
0.5-1.0 cm thick, bulb coats brown, somewhat reticulated at the base, clustered closely
together, attached to rhizome; stems 30-50 cm (rarely only 20 cm); leaves 2-4, mostly
basal or sheathing the lowermost part of stem, flat, 3-8 mm wide, linear, shorter than
stems; spathe 1 segment, early shedding; umbels relatively few-flowered, medium dense,
tending to droop to one side or laxly hemispherical, pedicels 1x length of tepals or
slightly longer, flowers openly bell-shaped, pure blue, tepals large at 11-14 mm long
(rarely up to 17 mm long) x 3.5-5 mm wide; stamens about 4/5 length of tepals.
Flowers August - September.
This
is one of the most beautiful and desirable blue alliums, with showy clusters of large true
blue flowers. Does not like hot, dry, sunny locations, and must have an open, well
lit location with adequate moisture. Can be found in cultivation, even though often
misnamed. A white-flowered form is grown in England. |
| 13b |
Flowers smaller, 6-10 mm, at least the margin of inner tepals are
minutely toothed |
| |
14a Inner tepals toothed, ends
of tepals rounded, spathe deciduous, leaves flat |
Allium
sikkimense - bulbs appear as narrow, thickened stem-bases,
cylindrical, 0.3-0.5 cm thick, bulb coats dark brown, fibrous and somewhat reticulated at
the base, clustered closely together, attached to rhizome; stems 15-40 cm (rarely only 5
cm); leaves 3-4, basal, flat, 2-5 mm wide, thickish, shorter than stem; spathe 1 segment,
early shedding; umbel hemispherical, dense, medium-flowered, pedicels short, less than or
equal to tepals, flowers bright blue, narrowly bell-shaped or bottle-shaped, barely
opening, tepals 6-10 mm long x 3-4.5 mm wide, bluntly rounded at ends, inner tepals
irregularly toothed (minutely toothed), stamens only 1/2 - 2/3 length of tepals.
Flowers July - September.
Another
excellent blue-flowered allium available in cultivation. It is often confused with
A. beesianum, however A. sikkimense is typically a much smaller plant only 15-20 cm tall,
with smaller, narrower, thicker foliage, and tight umbels of nearly closed bottle-shaped
flowers. Also appreciates a cool, moist position in loose, enriched soil, accepting
half shade to full sun. |
14b Inner & outer tepals
toothed (rarely only inner tepals), ends of tepals pointed, spathe persistent, leaves flat
with keeled underside. |
Allium
yuanum - bulbs solitary or clustered, appearing as thickened stem
bases, cylindrical, 0.2-0.4 cm thick, attached to a rhizome, bulb coats brown, somewhat
reticulated; stems 17-55 cm; leaves 2-3, narrow, 1.5-3 mm wide, strongly keeled on
underside, slightly shorter to slighter taller than stems, basal to slightly sheating stem
at base; spathe 1-3 segments, persistent; umbel hemispherical, dense, many-flowered,
pedicels about equal to tepals, tepals blue, irregularly toothed on all 6 tepals (rarely
just on the 3 inner tepals), sharply pointed at the ends; stamens 1/2 length of tepals.
Flowers August - September.
Very
similar to A. sikkimense, but differs markedly by the characteristics noted in the key.
Probably not in cultivation. |
| 12b |
Stamens exserted |
| |
15a |
Pedicels very unequal, 2-4 times length of tepals |
| |
Allium
heteronema - bulbs appear as narrow, thickened stem-bases,
cylindrical, 0.8-1.0 cm thick, attached to rhizome, bulb coats dark brown, strongly
reticulated and somewhat shaggy; stems 25-30 cm, rounded and angled in cross-section;
leaves 2-3, flat, 3-7 mm wide, widest at middle and slowly tapering to a point, midvein
evident, leaves more or less equal to stem, basal and sheathing base of stem; spathe 1
segment, persistent; umbel open and few-flowered, pedicels very unequal, 2-4 x length of
tepals, ascending with upright flowers in a flat-topped cluster, tepals narrowly
bell-shaped, purple-blue, 7mm long x 2-3 mm wide; stamens slightly longer than tepals
(exserted), style exserted. Flowers August. |
| 15b |
Pedicels nearly equal, 1-2 times length of tepals |
| |
Allium
henryi - bulbs appear as narrow, thickened leaf bases, cylindrical,
0.4-1.2 cm thick, bulb coats dark brown, strongly reticulated, persistent and shaggy;
stems 11-25 cm, finely angled in cross-section; leaves many, flat, 2-5 mm wide, widest at
middle and slowly tapering to a point, midvein evident, leaves taller than stem, basal to
barely sheathing base of stem; spathe 1 segment, persistent; umbel few-flowered, upright,
pedicels sub-equal, 1.5-2 x length of tepals, flowers held upright in a domed cluster,
tepals openly bell-shaped, purple-blue to blue, 5.5-7 mm long x 3 mm wide; stamens
slightly exserted to 1.5 x length of tepals, style exserted. Flowers September -
October. |
10b |
Leaves sheathing lower 1/2 of flower stem |
|
Allium stenodon
- bulbs appear as narrow, thickened stem-bases, cylindrical, 0.3-0.8 cm thick, attached to
rhizome, bulb coats blackish brown, fibrous, sometimes slightly reticulated; stems 20-50
cm sheathed for 1/2 the height with 2-4 leaves; leaves linear, flat, 2-3 mm wide, shorter
to equalling stem; spathe 1 segment, persistent; umbel hemispherical to nearly spherical,
densely many-flowered, pedicels 1-1.5 x legth of tepals, flowers openly bell-shaped, blue
to purple-blue, tepals 4-5 mm long x 2-3 mm wide; stamens well exserted, 1.5-2 x length of
tepals, style exserted. Flowers July - September. |
