Allium

1. Leaves usually over 2 cm broad, flat, petiolate, withering before the plant flowers.

2. Leaves with red bases (except for rare “albinos”), the widest usually 1.9–4 (–6) cm broad at 3 cm below the tip; larger umbels with ca. (13–) 18–40 (–60) flowers, flowering from the last few days of June through early August.

A. tricoccum

2. Leaves lacking red bases, the widest (0.6–) 1–1.7 cm broad at 3 cm below the tip; larger umbels with ca. 7–17 flowers, flowering in June.

A. burdickii

1. Leaves linear, flat or terete, less than 2 cm broad (usually less than 1 cm), not petiolate, present at flowering time.

3. Umbel nodding, on bent or reflexed tip of scape; leaves flat.

A. cernuum

3. Umbel erect on straight tip of scape; leaves flat or terete.

4. Leaf blades terete, hollow, at least most of their length [These flattened where pressed in drying, but the base of blade, just above summit of sheath, will not show 2 distinct surfaces].

5. Stem stout, over 5 mm in diameter for most or all of its length, distinctly inflated below the middle.

A. cepa

5. Stem 5 mm in diameter or less (very rarely as stout as 7 mm), without inflated section.

6. Pedicels equaling or shorter than the flowers; inflorescence without bulblets; filaments unappendaged.

A. schoenoprasum

6. Pedicels longer than mature flowers; umbels bearing bulblets in addition to 0–many flowers; inner filaments with a long slender appendage on each side.

A. vineale

4. Leaf blades flat (sometimes keeled).

7. Umbels bearing bulblets (flowers few or none).

8. Involucral spathe composed of 2–3 bracts, the longest with a beak less than 1.5 cm long; native species of forests, floodplains, stream banks, or meadows.

A. canadense

8. Involucral spathe composed of 1-3 bracts, the largest with a beak usually 2–10 cm long; weeds of disturbed habitats.

9. Involucral spathe of 1 bract only; flowers (if present) with stigmas not exserted beyond petals at maturity; bulb with whitish papery outer coverings.

A. sativum

9. Involucral spathe of usually 2-3 bracts; flowers (usually present) with stigmas clearly exserted beyond petals at maturity; bulb with brownish, ± fibrous outer coverings.

A. carinatum

7. Umbels not bearing bulblets.

10. Flowers white; umbels flat-topped to hemispherical, flowers all facing up while in bloom; flowering mid-August through October.

A. tuberosum

10. Flowers pink to purple, umbels ± spherical, flowers facing in all directions; flowering June through early August.

11. Leaves all at base of plant; filaments slender, unappendaged; ovary with thin erect projections or crests at the apex.

A. stellatum

11. Leaves scattered on lower half of stem; inner filaments broad and flat, trifid, with a long appendage on each side extending beyond anther-bearing central filament; ovary without crests.

A. rotundum

All species found in Allium

Allium burdickiiWILD LEEK 
Allium canadenseWILD GARLIC 
Allium carinatumKEELED GARLIC 
Allium cepaONION 
Allium cernuumNODDING WILD ONION 
Allium rotundumONION 
Allium sativumGARLIC 
Allium schoenoprasumCHIVES, WILD CHIVES 
Allium stellatumWILD ONION 
Allium tricoccumRAMPS, WILD LEEK 
Allium tuberosumCHINESE CHIVES 
Allium vinealeFIELD GARLIC 

Citation:

MICHIGAN FLORA ONLINE. A. A. Reznicek, E. G. Voss, & B. S. Walters. February 2011. University of Michigan. Web. October 24, 2017. http://michiganflora.net/genus.aspx?id=Allium.