I have a lace java fern attached to a small (3-4 inch) rock. There are probably about 6 plants on the rock; they all grew from one root or tuber. I got them a year ago and it took them this long to grow about 4 inches tall. I have thinned them out a little; many new plantlets grow from the root area, and I've trimmed out a few leaves. I've left the roots on the rock alone.