Hydrangeas grow 4 to 12 feet tall depending on the variety. They produce large, pink flowers in soils with a pH between 6.5 and 7.0 and blue flowers when the soil pH lies between 5.0 and 5.5. The plants, depending on the cultivar are hardy down to USDA zone 3, where temperatures stay above -30 degrees Fahrenheit. Other cultivars are only hardy down to zone 5 where the temperature stays above -10 degrees. Check your plant's hardiness before planting. Knowledge of how to create the right environment for the plant will help you produce a healthy and thriving shrub.
Choose an area to plant the hydrangea with full sun the morning and shade in the afternoon. Make sure the spot has well-drained soil. Before planting, dig 1 to 2 feet into the ground with a spade, breaking up clumps of soil, and mix in a healthy amount of organic compost.
Plant the hydrangea in spring or fall, when the weather is cool. Setting the plant out in hot weather will place excessive strain on the plant. Space multiple plants 6 to 12 feet apart, depending on the size of the cultivar.
Water the hydrangea deeply after planting. Place a 2- to 3-inch layer of mulch around the base of the plant. This will protect the roots from hard frosts and keep the soil evenly moist.
Water deeply once a week or more in hot weather. The big leaves of this plant means that it loses more water through transpiration.
Fertilize after growth starts and in May and July for optimal growth. Use an all-purpose fertilizer marked 10-10-10 and follow the directions on the package for application instructions. Each brand will have different directions.
Prune the hydrangeas back right after flowering if necessary. Cut out any weak, damaged or dead branches with pruning shears.
Provide winter protection for the hydrangea. Place more mulch down to protect the shallow roots. Lay a blanket or tarp down over the shrub and stake the corners down to protect the leaves. These measures will help your hydrangea recover more easily in the spring.