Hydrangea is a large genus of flowering perennial shrubs belonging to the botanical order rosales. Hydrangeas come in many dozens of species, varietals and hybrids, and feeding preferences vary among the main species. To achieve optimal performance from your hydrangea, feed according to the species' needs, and water and mulch liberally.
Feed big-leaf varietals of hydrangea with an all-purpose formula lightly three times throughout the growing season in the early spring, early summer and early fall. Apply according to product label dosing directions being careful not to exceed 1 pound of fertilizer for every 100 square feet divided among the three feedings.
Fertilize varietals of panicle and oakleaf hydrangea plants twice per growing season with a balanced formula with a half-pound per 100 square feet of soil in each fertilizing session. Make the first half-pound feeding in spring and the second in early summer.
Feed smooth leaf hydrangea varietals once every year in the late winter with a balanced water soluble formula and apply in a dose commensurate with the label recommendations.
Determine bloom color on your big-leaf hydrangea plant by choosing the fertilizer or amendment that cues blue or pink flowering. Use fertilizer low in phosphorus to grow blue flowers. Use a balanced phosphorous formula to produce pink hydrangea blooms.