Late spring is a good time to \"pinch back\" or shorten the new growth of summer blooming perennials like mums, sedum autumn joy and liatris. I use scissors or pruning shears to shorten each stem by at least half or even by two-thirds. Cut back to a node or joint in the stem just above a pair of leaves. This will encourage branching and a shorter, more bushy plant that is less likely to flop or need staking. Keep Growing, Marianne Binetti