Per WIKIPEDIA: 'Allium is the onion genus, with about 1250 species, making it one of the largest plant genera in the world. They are perennial bulbous plants that produce chemical compounds (mostly cystein sulfoxide) that give them a characteristic onion or garlic taste and odor, and many are used as food plants. Allium is classified in family Alliaceae although some classifications have included it in the lily family (Liliaceae). Allium species occur in temperate climates of the northern hemisphere, except for a few species occurring in Chile (as Allium juncifolium), Brazil (Allium sellovianum) or tropical Africa (Allium spathaceum). They can vary in height between 5 cm and 150 cm. The flowers form
an umbel at the top of a leafless stalk. The bulbs vary in size between species, from very small (around 2-3 mm in diameter) to rather big (8-10 cm). Some species (such as Welsh onion, A. fistulosum) develop thickened leaf-bases rather than forming bulbs as such. Most bulbous alliums increase by forming little bulbs or "offsets" around the old one, as well as by seed. Several species can form many bulbils (tiny bulbs) in the flowerhead; in the so-called "tree onion" (A. cepa Proliferum Group) the bulbils are few, but large enough to be used for pickling. Members of the genus include many valued vegetables such as onions, shallots, leeks and herbs such as garlic and chives. A strong "oniony" odor is characteristic of the whole genus, but not all members are equally flavorful. Some Allium species, including A. cristophii and A. giganteum, are used as border plants for their flowers, and their "architectural" qualities. Several hybrids have been bred, or selected, with rich purple flowers. Allium hollandicum 'Purple
Sensation' is one of the most popular and has been given an Award of Garden Merit (H4). By contrast, other species (such as the invasive Allium triquetrum) can become troublesome garden weeds.' End quote.
Flower
Plant location: Found on a hike in the Pawnee National Grasslands - Pawnee Butte, Trail #840 on May 26, 2008. This was an excellent hike for sighting wildflowers!! We identified no less than TWENTY-FIVE new species of wildflowers on this hike. Having just moved to Colorado, this was a wonderful introduction to the Plains wildflowers of Colorado. We highly recommend the hike. The area is also known for it's raptor population.
Plant
Bloom season: Generally early spring through June. Some species like the cooler weather. They die back as it gets hotter and then bloom again in the fall.Foliage
Wild Onion (Allium geyeri), family Liliaceae
Flower 
Plant location: Found on a hike in the Pawnee National Grasslands - Pawnee Butte, Trail #840 on May 26, 2008. This was an excellent hike for sighting wildflowers!! We identified no less than TWENTY-FIVE new species of wildflowers on this hike. Having just moved to Colorado, this was a wonderful introduction to the Plains wildflowers of Colorado. We highly recommend the hike. The area is also known for it's raptor population.
Plant 
Bloom season: Generally early spring through June. Some species like the cooler weather. They die back as it gets hotter and then bloom again in the fall.Foliage