I've heard them called ephemerals. Indeed, they tend to be small, bright, and short-lived. They sprout on the forest floor, peaking out from beneath leaf litter, or tucked between tree roots or along streams and vernal pools. Here are some that greeted me from April 20 -22 on forays into the woods of a western Pennsylvania town, McMurray, PA.
Please see my native plant series to learn which to plant right now and where to find them.