Improve the soil prior to planting by adding plenty of well-rotted manure or garden compost, adding mycorrhizal fungi (Root grow) to aid establishment. Hydrangeas do not like to dry out so keep them well watered during hot, dry weather. If they do start to suffer, soak the roots with a hose and they will usually recover. Remove faded flowerheads in spring after the danger of frosts, cutting back the flowered stems to a strong pair of buds. Take out misplaced or diseased shoots. Mulch young plants with well-rotted manure or compost in spring. Once established, remove a quarter to a third of the shoots to the base of the plant.