Several coral bells (Heuchera) in my garden are 1 to 3 years old. On a few of them, the crown of the plant seems to be moving up, out of the ground. Since our last couple of winters have been mild, I wouldn’t think that it is due to frost heave (also, none of my other perennials have heaved). Since the plants now seem to be rather flimsy, should I replant them, lowering the crown to soil level? Did I do something wrong when I initially planted them or is this a characteristic of the plant?
You probably did nothing wrong when you initially planted your coral bells. They are a perennial that ages quickly. It is the characteristic of their crowns to move to the soil surface and to die out in the center of the clump. As a result you see their spindly growth and flimsy appearance. The ones that appear to be heaving are probably the older plants. Heuchera benefits from timely division and replanting every 3 years. In the spring, carefully remove the individual plants, checking the crowns for rot. Also look for small white grubs in the soil under the plants, as well as in the crown. Those are root weevil grubs and they enjoy feasting on the crowns. Cut away any portion that appears unhealthy, leaving a leaf bud or leaves, stem and some root for each division. If root weevil grubs are present, manually clean them from the soil, and rinse the plant roots in water. Rinsing the crown may also dislodge slug eggs, which look like translucent orbs the size of small peppercorns. Slugs have an uncanny ability to leave their eggs in places tightly clustered and evergreen, like the coral bell crowns. Unfortunately, rinsing and squishing the offenders won’t get all the ones who have eluded you in the soil. If at all possible, try to relocate the divisions to a new area. If this is not possible, remove 2 to 3 inches of soil and replace with clean, well-drained soil in the planting area.