Pruning pampas grass Perenniel grasses are usually left unpruned in autumn to provide winter interest. If winter winds and rain or snow break them and make them look untidy, they can be trimmed as needed to produce a neat plant. Every year cut and comb out old stems and dead leaves, wearing protection for your arms and hands because grasses can cut you quite badly. If you want to control the size of the clump, in late winter or early spring use shears to cut back just above ground level. If you are growing the grass where it is marginally hardy, wait until late heavy frosts are no longer likely to occur, because the old growth serves as protection for the new growth areas.
