Allium bulbs should be planted in fall, after the first frost and before the ground freezes. Planting after the first frost creates the perfect conditions for planting allium and other small bulb plants. The ground will be warm enough for the bulbs to establish roots, but not so warm that they'll mistake the fall for spring and create shoots. Keep in mind that not all alliums grow from bulbs! A few, called herbaceous allium, multiply through root clumps like perennials. Herbaceous alliums include allium tuberosum--better known in the vegetable garden as garlic chives--Millenium, Snowcap, and prairie onion varieties. Alliums that grow as perennials can be planted in either spring or fall.