Q. My ornamental grasses are still in place in my yard. They looked nice all winter. When and how do I cut them back? When do I divide them?
–Fleet Walker, Nashville, Ind.
A. Ornamental grasses can be cut back any time from fall to spring, but I like to leave them in place over the winter. They bring motion and texture to the garden when they’re desperately needed! By late winter, heavy snows and ice start to break the grasses though, and that can create quite a mess in the yard. In February or March, I head outside with pruners or electric hedge shears and start cutting the larger grasses back 4 inches from the ground. Some gardeners tie the tops in a bundle with twine or duct tape to make clean up easier. Smaller grasses, like fountain grass, can be cut even closer to the ground, leaving 1 inch of stubble. Fine-textured grass like fescue can actually be sorted through with your fingers. The brown strands will separate easily, leaving the still-blue-green blades in place.
Divide the grasses when growth begins. Cool season grasses, like feather reed grass (Calamagrostis), begin growth in March, so watch for the first sign of greening. Warm season grasses, like fountain grass (Pennisetum), maiden grass (Miscanthus) and hardy pampas grass (Erianthus), begin to produce shoots later in May. When the grass has grown a few inches, lift the clump from the ground and divide it into several sections with your shovel, knife or saw. Reset the divisions at the same depth in their new locations.
Q. I have a tree peony and would like to know when is a good time to transplant it and how to do it.
–Pat, Covington, Ind.
A. Fall is the ideal time to transplant all peonies. Prepare the new site by adding organic matter and loosening the soil. Dig the tree peony with as large a root ball as possible and try to maintain contact of the soil to the roots. Plant the peony in its new site at the same depth as the original site. Add a layer of mulch for winter protection. Next year, water and fertilize to help it recover. Transplant shock still may ensue, so expect a reduction in blooms for a year or two.
Q. I have heard that there is a spray you can use on iris beds that will kill the grass but not harm the iris rhizomes. It is impossible to pull the grass out and get the roots.
–Amy Houser, Pleasant Lake, Ind.
A. Fusilade II is labeled for use on iris. It’s the active ingredient in Ortho’s Grass B Gone, as well as other products. Check the label of the herbicide that you purchase to make sure it’s labeled for iris. Always read and follow label directions carefully.