Hydrangeas are easy to grow when planted in the right USDA Zone, the right exposure to sunlight, the right soil, and with proper fertilization. Though some varieties will tolerate more sun, for peak performance, most prefer afternoon shade, particularly in the hotter regions of the South. Moist, but well-drained soil is a must. Azaleas, camellias and rhododendrons will not tolerate wet feet. Humus-rich, fertile soil is preferred.
Best Growing Conditions
Sun - The amount of sun a hydrangea needs or will tolerate depends on your location. In zones further (6-4) many types of hydrangeas can and will tolerate all day exposure to direct sunlight. In zones further south (7-9) most varieties of hydrangea will appreciate a break from the sun during the hottest part of the day. When in doubt about the sun needs for a specific variety of hydrangea consult with with your local nursery and garden center or whoever you purchased the plant from.
Soil Type Preferred - Hydrangeas grow best in well-drained, moist, fertile soil that is rich in organic matter, but tolerate a wide range of soils as long as water and nutrients are not limiting and soil pH is adequate. They are tolerant of heavy clay soils if drainage is good. In soil with low fertility or compact clay it'll be worth your time to mix in some organic compost to the native soil. They like the soil to hold a good supply of water, especially when plants are in full bud and blooms are developing, but not so much water that the soil stays constantly soggy or wet.
Soil pH Preferred - Hydrangeas will tolerate a wide range of soil pH anywhere from 5.5 to 7.5 on the scale. However, the pH of the soil can effect flower color on some types of hydrangea, particularly some varieties of the mopheads (Hydrangea macrophylla). Whenever growing plants that prefer a specific pH it's a good idea to test the soil. Testing kits are available at most local nursery and garden centers or you can buy soil test kits online here. Your local Extension Service might provide soil testing services as well. Depending on the results of the soil test, you can add lime to raise the pH or soil sulfur to lower the pH (make more acid).
Type Of Fertilizer
NOTE: If you purchase and plant your hydrangea when it is dormant during winter, wait to fertilize until you see new growth begin to emerge in spring.
At Planting Time - If you purchased your hydrangea from a nursery and garden center, and the plant looks very healthy with dark green foliage, chances are it has been fertilized. If I used an organic soil amendment to condition soil at planting time, especially one made from composted manure, I usually just water the plant with a solution of root stimulator (containing Vitamin B1) as this will help promote vigorous root development. Additionally, if it appears that the plant was not fertilized well in the container it was growing in, after planting I'll usually broadcast an organic or well-balanced, slow-release shrub and tree fertilizer on top of and around the perimeter of the rootball. Follow instructions on product label for application rates.
Therafter - After plants have become established, an application of a well-balanced, slow-release shrub and tree fertlizer is usually enough to last the entire year. When using mild, organic plant foods, feed plants in late winter or early spring and again in early summer.
How to Change the Color of Hydrangea Blooms
Hydrangeas are fascinating in that, unlike most other plants, the color of their flowers can change (or be changed) dramatically. But this doesn't happen as easy as many think, and not all types of hydrangeas have blooms that can or will change color. White-flowering hydrangeas will not change color, though some fade to shades of pink or red in the fall. The ones that will change are primarily the pink and blue Hydrangea macrophylla varieties, or what some commonly call "mophead," "snowball" or "French" hydrangeas.
It's easier to change the color of hydrangeas when they are being grown in containers verses growing them in the ground. This is because the soil pH is easier to adjust in a contained environment, and it is pH adjustment that changes the color of the blooms.
Sometimes, after planting a hydrangea in your yard, a hydrangea will change color on its own when adjusting to the new environment. While it's going through this adjustment, it's not unusual to see several different colors on one shrub the next year after planting.
It is much easier to change a hydrangea from pink to blue than it is from blue to pink. Changing a hydrangea from pink to blue requires adding aluminum sulfate to the soil, which makes the soil more acid. Changing from blue to pink means subtracting aluminum from the soil, which can be done with applications of lime. Apply lime several times a year until you've achieved the desired color.
Watering Hydrangea
Hydrangeas prefer a moist but well-drained soil. Constantly soggy soils can stunt growth and cause root problems that can lead to the death of the plant. During the first warm season after planting make sure to provide adequate water when plants are establishing their root system. During the cool season, when plants are dormant, there won;t be as much a need for water. Therafter, when plants are established, in the absence of regular rainfall provide water as needed to keep soil moist during dry periods.
