Caring for Hydrangeas
Hydrangeas are a beautiful yard plant, with large, thick foliage and large blooms of flowers either throughout the summer or from mid to end of summer. There are many different varieties of hydrangea, and each has its own watering and sun needs. Make sure you research the particular needs of each variety available before you select one, especially if you already have a site planned out in your yard.
Hydrangeas require rich soil, plenty of water, and sunlight to grow and bloom properly. In northern regions, grow hydrangeas in full sun to ensure proper blooming. Shade will not kill the plant, but it will cause few to no blooms to be produced. In southern regions, grow hydrangeas in partial shade where they will be protected from afternoon sun. Bigleaf, oakleaf, and smooth hydrangeas will tolerate more shade than panicle hydrangeas. Plant hydrangeas so that the top of the root ball is right below the soil surface. Water thoroughly for several weeks after transplanting, especially in summer.
Hydrangeas love water, but must be planted in well-draining soil to prevent root rot. They should be watered deeply about once a week. In very dry conditions, water more often. When a hydrangea plant is thirsty, its stems will sag, letting you know it needs more water. In hot conditions, check the plant in the evenings, as midday heat will also cause drooping.
As with many other plants, too much or too little fertilizer will be equally damaging. Fertilize your hydrangea plant no more than twice per year, in early spring and early fall. Be especially careful in your application of nitrogen, as it will cause stems and leaves to grow quickly and can limit the nutrients that are available to be used to produce blooms. The quick growth will be weak and vulnerable to disease or weather damage. Limit nitrogen applications in early fall to prevent new growth from being produced right before winter. Whenever you fertilize, make sure to keep fertilizer away from the foliage of your plant, as it will burn and kill the leaves.
Pruning is not essential but will encourage thick growth. If you do choose to prune, a suggested guideline is to remove about one-third of old growth each year. The type of hydrangea you are growing will determine when you can prune without losing next year's blooms. Some varieties of hydrangea bloom on new wood, some bloom on old wood, and some bloom on both. Bigleaf and oakleaf hydrangeas form their buds for the following year in late summer, so pruning must occur by midsummer, as soon as possible after the blooms begin to fade. Panicle and smooth hydrangeas form their buds on new growth, so they can be pruned anytime after the blooms are done, from late summer until growth starts the following spring.
Altering soil pH to change bloom color
The color of pink and blue varieties of hydrangea blooms is determined by the amount of aluminum the plant is able to intake, and the aluminum intake is determined by the pH of the soil. A pH below 5.5 is acidic and will increase aluminum intake to produce blue blooms. A pH of 6.5 or above is neutral to alkaline and will usually produce pink blooms. A pH between the two numbers will produce purple blooms. It is possible to have both pink and blue blooms on the same plant, or even within the same bloom.
To help increase the available aluminum and produce bluer flowers, you can mix aluminum sulfate with water (about a tablespoon per gallon of water) and apply the mixture to the soil in early spring. A hydrated lime solution (one tablespoon per gallon of water) will help create more alkaline soils to produce pinker flowers.
Given the correct soil and sunlight, hydrangeas are easy, low-maintenance plants that will liven up your yard throughout the summer. For more information on hydrangeas or other plants to make your home and garden beautiful, come into your local Menards® Garden Center!