Q: Two years ago I planted a section of a perennial bed with half a dozen plants of a gorgeous blue fescue, but they haven’t filled in as I had hoped. Do they need richer soil, less sun, or what? — FranzdeBerry, Springfield, Ill.
A: A little tough love is all they need. Though the blue fescues look as rugged as wire, they actually benefit from more frequent division than most ornamental grasses require. Once every three years (in the spring, not in the fall) is a healthy interval. Blue fescues are naturally short-lived, and division rejuvenates them. Left alone, clumps often develop dead centers. First dig the whole patch and set the clumps aside so you can work the soil, preparing a smooth bed. Tear each clump in half, and then break off divisions (about 2 to 3 inches across) for replanting. Place them in the garden bed 8 to 10 inches apart, and water them immediately. Fescues grow best in soil that’s very well-drained. A layer of fine gravel is an excellent mulch; organic mulches keep the soil too damp. Regular watering encourages divisions to re-establish roots quickly, but be sure to let the soil dry out between waterings. This is especially important if you have clay soil, because fescues are prone to rot.