Mophead hydrangeas (Hydrangea macrophylla) grow 3 to 6 feet tall and 6 to 10 feet wide, producing pink, white or blue ball-shaped flowers in summer. Adapted to U.S. Department of Agriculture plant hardiness zones 5 through 9, depending on the cultivar, this plant thrives on little care. It likes full sun and partial shade in hot climates, as well as well-drained, but moist soil. A little attention can keep this shrub in check and flowering bountifully.
Water a newly planted hydrangea regularly, keeping the soil slightly moist, until it starts growing vigorously on its own. Once established, water the hydrangea only during extended droughts of a two or three weeks, drenching the soil around the plant for a few minutes once a week until it rains. Plants in full sun may need more water than those shaded for part of the day.
Scatter half of a tablespoon of 5-7-2 organic granular fertilizer around the base of the hydrangea for every square foot of the canopy in spring and fall. Hydrangeas bloom best when slightly stressed and this low-nitrogen formulation will provide just the nutrition the plant needs.
Prune the bush right after flowering ends with pruning shears, choosing overgrown branches and cutting them back to within the canopy or to the ground. Mophead hydrangeas bloom on old growth, so pruning at any other time will limit the number of blooms for the following season. Clip off faded flowers as well at this time.
Check periodically for signs of disease and pests on the bush. Hydrangea is particularly susceptible to slugs and aphids, which you can get rid of with a blast of water from the hose. Mopheads may also contract powdery mildew and leaf spot, which are unattractive, but will not likely kill the plant.
Things You Will Need
- 5-7-2 organic granular fertilizer
- Pruning shears
- To change the color of the mophead hydrangea flower, you must change the pH of the soil. Add aluminum sulfate if you want to lower the pH to get a blue flower and add lime to raise the pH for pinker flowers.
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