Dans Papers - June 8, 2007 - The Garden At Rock Cottage

I marvel at how quickly hydrangeas leaf out and set blooms each season. This versatile flowering shrub can provide a dramatic display when grouped and also works well as a single specimen. The large, complex flower heads come in colors from dark blue, to red, purple and white.

The name Hydrangea comes from a compound Greek word meaning "water-vessel." This refers to the roots that store a large quantity of water. While the name is Greek, the plants seem to have origins from several world locations including the Himalayas, North and South America and Central and Eastern Asia. Native Americans cultivated the plant as a curative for infections, arthritis and other ailments common to an aging population. The leaves were dried and used as a substitute for tobacco - and reportedly have a slightly narcotic effect.

The flowers themselves are of three main types - mophead, panicle and lacecap. Mopheads produce globe-shaped flowers that can be as large as a foot in diameter. The panicle-flowered varieties produce elongated, conical-shaped flowers up to 14-inches long. Lacecaps produce disc-like flowers about 6-inches across with florets that appear only at the circumference and have colored, seed-like nodes at the center.

In addition to being classified by flower type, there are five main categories of hydrangea frequently seen on the East End. These include the Smooth Hydrangea (H. arborescence) that produces a five-foot shrub with oval, gray-green leaves and dull white flowers, the Oakleaf Hydrangea (H. quercifolia) with deeply lobed, oak-leaf shaped leaves on a six-foot shrub with white, panicle flowers, the Climbing Hydrangea (H. anomala) that produces a large vine with shiny-green leaves and numerous white flowers, Peegee Hydrangea (H. paniculata) that can produce a shrub up to 20-feet tall with white flowers that fade to pink and French Hydrangea (H.macrophylla) that produces a mounding shrub up to six-feet tall with either pink or blue flowers. A sixth rare variety, Ayesha, is a fragrant shrub introduced shortly after World War II. It produces delicate pink to mauve flowers that have a waxy consistency - just beautiful and one of my favorites.

Hydrangeas are easy to grow. They respond extremely well to a little cultivation and protection from deer that find the leaves an irresistible salad. Deer can consume the leaves and flowers from an entire clutch of hydrangeas in one evening.

Because the shrub likes moist but not wet soil, it benefits from a site that is partly shady and that has enriched organic soil. French hydrangeas tolerate more sun that the others, but most prefer a situation with some light morning sun and afternoon shade. The shrubs benefit from regular feeding with cow manure or a multi-purpose fertilizer. They also benefit from plenty of water to keep the roots moist, but not wet or soggy.

Among some species, flowers can be forced to change color based on the amount of aluminum acidity in the soil. French hydrangeas produce blue flowers in acidic soils where aluminum is present. Flowers will be pink in more neutral soils where they absorb less aluminum. For some white-flowered, male hydrangeas, altering the pH of the soil can change the eye color.

To produce deep blue flowers, sprinkle aluminum sulfate around the roots to increase acidity. About a half-cup per 15 square feet of soil works well. To make the flowers pink, spread a cup of dolomitic lime over the same area. It takes almost a full season to see noticeable color change. Spreading spent coffee grounds around the plants also tends to enhance the blue color and may add to plant vigor.

Hydrangeas sometimes fail to bloom. This has two causes - winter damage or pruning at the wrong time. On most hydrangeas, prune plants immediately after blooming, but never later than the first week in August. Too much nitrogen from over-fertilizing will produce abundant leaves and no flowers.

Every garden on the East End ought to have at least one representative hydrangea. How would summer flower arrangements survive without them?