Hydrangea pruning: Lacecaps and Mopheads. These are treated very differently to arborescens or paniculata as they flower on old wood. First up, remove one or two of the oldest stems from the base, or if it hasn't been pruned in a long time and it's really congested as shown here, remove up to 30% of the old wood to the base. Remove dead, diseased and damaged stems also. Finally, prune all dead flowerheads back to the first strong pair of buds back from the flower head. You should be left with a