If you're a home gardener of any experience, you already know that impatiens are a shade-lover's dream. But flashy hydrangeas, with their huge pom-pom flowers six to 10 inches in diameter, are another tradition in shade-laden areas. And they're at full bloom through summer.
Hydrangeas feature their huge globe-shaped flowers in pink, white, red and blue. Their biggest prerequisite is shade or filtered sun, and plenty of water on our hottest days. Besides providing an abundance of color in shady areas, hydrangeas fill an important niche in the garden.
For instance, as shrubs go, they bloom for a long time - literally all summer. They're versatile in that you can keep them pruned to manageable size or let them go to rather gigantic proportions. Most gardeners probably keep hydrangeas in the four- to eight-feet range. Hydrangeas are also deciduous in that they lose their leaves in winter. Therefore, they are perfect as a background planting, and are ideal companions to azaleas, camellias and rhododendrons.
Yet, my favorite reason for growing hydrangeas is their interesting ability to change color according to the pH level of the soil. There aren't many plants that you can change the color of flowers by fertilizing. Plus, there aren't too many blue flowers with 10-inch heads. In order to make flowers a deeper blue, they can be fed with aluminum sulphate (or even turn pink shades into blue). This forced feeding needs to take place a couple times in early spring and spring. You can also change flowers to a deeper pink by feeding with garden lime in spring.
The most widely grown garden varieties are the big-leaf hydrangeas or Hydrangea macrophylla. There are two types of big leafs: hortensias and lace-caps. Hortensias are the most common, and they are the types with the huge globe-shaped flower heads. The lace-caps have disc-shaped flower heads with tiny perfect flowers and an outer ring made up of larger flowers. Many home gardeners have come to love the lighter, more natural look of the flat lace-cap types.
Two cultivars of lace-caps include Bluebird and Blue Wave. Both retain their blue flowers in soils that have a higher pH (approaching 7). As mentioned, hydrangeas vary in their reaction to chemicals in the soil. In acid soils (pH less than 7), most cultivars make blue flowers. As the pH decreases, the aluminum in the soil becomes more available and hydrangeas take up more. It's always kind of fun to feed hydrangeas to see what shades of blue or pink you can come up with.
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