In the past 10 years that I've grown Erythronium americanum, all it ever does is make leaves, never a single flower in all that time. The diffusely mottled fleshy foliage is delightful, the rhizomes spreading the colony around, but I want flowers! I noticed today it is starting to spread into my lawn.
It is planted in sloped bed under a Magnolia tree where I have lots of trillium species, cyclamen, and a tiny Viola species. The Erythronium and Viola are benign spreaders, too small to harm the commingling Trillium and Cyclamen.