Showy hydrangeas can be the showpiece of any garden or landscaped area, but they do require special care as the color of the flower is directly affected by the acidity of the soil, and while they require sun, the amount is dependent on the region. Hydrangeas come in many varieties, the most common being mopheads or lace mopheads, both of which have large, mounded clusters of flowers and big leaves. The lace variety is a bit daintier. Hydrangeas are also available as climbing vines, hardy oakleaf, on which the leaf changes color as the weather cools, and panicle, on which flower clusters are cone-shaped, rather than round.
Plant hydrangeas in full sunlight, unless in a hot-summer or tropical climate, where they require at least some shade to withstand the summers. Particularly in the deep South and Florida, hydrangeas should be planted in near total shade to withstand the humid, hot summers. According to Sunset's National Garden Book, hydrangeas do best in zones 2-8.
Water your hydrangeas often and liberally. If a hydrangea is wilting, it needs a drink, and just like people, by the time it's thirsty, it's a little too late. To avoid hand-watering daily, install a drip water system.
Prepare soil for hydrangeas by adding compost and water-retaining mulch. Hydrangeas need moist, rich soil for best results. If the soil in your garden is not rich, feed your hydrangeas with an all-purpose plant food (10-10-10) and a one-time fertilizer.
Pick your color. Hydrangeas will change color based on the amount of acidity in the soil. Garden soil with high acidity will produce vibrant blue-violet blooms, and garden soil with high alkalinity will produce blooms from light to hot pink. You may alter the acidity of your soil by either adding aluminum sulfate to create blue flowers or lime to create pink flowers.
Deadhead hydrangeas with blooms are spent by pinching or snipping the bloom off just below the head any time. You may also prune dead wood any time.
Prune your hydrangeas using a small hand pruner to promote growth at the end of the season. Cutting back the dead blooms and completely removing the dead wood once the blooming season is over will promote more and heartier blooms for the next season.
Plant hydrangeas in the fall or early winter in more temperate climates to establish root growth. In colder climates, plant as soon as the ground is ready to allow ample time for the root system to develop.