The beautiful hydrangea comes in shrubs and climbing vines, and can be pruned to become hedges or trees that grow up to 20 feet high. Some hydrangeas are native to East Asia, while others originated in eastern United States. The popular Grandiflora variety can tolerate temperatures of minus 30 degrees Fahrenheit in Zone 3. The oakleaf variety, native to the American Southeast, is hardy to Zone 5.
Where to plant
If you live in the north, your hydrangea will need more sun. They do not thrive in heavy shade under the umbrellas of hardwood trees.
With enough moisture, most hydrangeas can take sun all day; they need five hours a day.
The blooms of the oakleaf hydrangea last longer in hot climates if it gets afternoon sun. The oakleaf gets root rot easily so it needs well-drained soil.
If you buy a hydrangea, you can plant it any time of year. You should buy it while it is in bloom so you can see what you're getting.
It's best to plant hydrangea in the spring or fall when there is no danger of frost. Do not plant in the heat of summer. Give it at least 4 feet in all directions. Plant it in drained soil, not too close to a tree with a root system that can rob it of nutrients.
If you have heavy soil, add roughage such as pine bark mulch to help loosen it. If you have clay soil, take care not to overwater your hydrangea because it can lead to root rot.
Transplant your hydrangea when it is dormant. Dig up as much of its root ball as possible and transplant it to an area with afternoon shade. Water it deeply once, then wait until spring. You'll need to water the well the first two summers. If the soil is moist but the leaves wilt, mist your hydrangea daily until it recovers.
Fertilize once or twice in the summer, but not if the plant is wilted or looks sick. You can use compost or a slow-release 10-10-10 fertilizer.
Apply fertilizer to the drip line of the branches, not next to the trunk. Use one-eighth to one-fourth of a cup of fertilizer for a small plant and 2 to 3 cups for mature hydrangeas.
Do not fertilize after August; your hydrangea needs to prepare for dormancy. A May and July application are about right for the South. A single dose of fertilizer in June or July is good for the North.
Water hydrangeas deeply with a hose. Do not let the soil get soggy. The roots of some varieties of hydrangeas rot easily.
Oakleaf hydrangeas produce buds on stems that have been on the plant since the previous summer. Remove all dead wood each year. To revitalize the plant after it is 5 years old, cut a third of the branches to the ground each summer. If you think you need to reduce its size, cut it back in June or July.
The Paniculata cultivars, including Annabella and Peegee, bloom every year on new stems. Do not prune them in the spring or summer when they are getting ready to bloom. You can prune Paniculatas in the fall, winter or spring, but you don't have to trim them every year. These grow as shrubs, but you can prune them as trees by leaving a trunk and not removing top branches.
For flower arrangements, cut with long stems in June or July. It is better to cut them with short stems after August.