Summer snowflake (Leucojum aestivum) needs full sun to partial shade and moderate moisture conditions to reach a height of 18 inches. A native of Europe and southwest Asia, this bulb produces a flowering stalk with one to two nodding white flowers with green markings, and it has several strap-like leaves. Reliably hardy and long-lived in Chicago-area gardens, summer snowflake has been in cultivation long enough to be an indicator of abandoned homesteads. It normally blooms in mid-April and goes dormant by midsummer.