You need to dig them up every few years and separate the bulbs, like iris. Some of them popped up at a house I bought. I started to dig them up in the fall, and found a patch as big as a kid's wagon packed solid with bulbs. They ended up lining my sidewalk. The leaves come up before anything else, then are dying back about the time I first mow the yard. Just mow over them, then late July/early August the flower stalks pop up.