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The Plant Doctor: Soil determines colors of hydrangea’s blooms

By Harvey Goodman

Imagine creating a plant that changes color from, let’s say, white to pink to blue just by adding material to the compost surrounding the plant. Our ideal plant not only changes color but is equally decorative in a greenhouse, window, terrace or garden. With a wave of the proverbial wand we introduce you to the ever-popular hydrangea.

Bought to Europe and eventually the United States in the 1900s, hydrangea grows wild along the riverbanks in China and Japan.

The name “hydrangea” gives us a clue to the needs of this plant. “Hydro” from the Greek word for “water” and “angion,” meaning “tub,” describe a plant that loves humidity and plenty of water. While we are on the topic of names, the hydrangea is also referred to as Hortensia, a totally unscientific term named after the girlfriend of the French botanist Philbert Commerson, who first described the plant.

The most popular hydrangea is H. macrophylla. Its popularity is established from its ability to produce flowers that change color based on the acidity or alkalinity of the soil. In neutral soil the flowers are white. In acid soil they turn pink, and in basic or alkaline soil they are blue. This occurrence brings back memories of the high school chemistry laboratory where litmus paper was used to determine the pH of a solution.

When purchasing the plant, look for one with large green leaves and stalks. Plant the bush in a light, cool spot in compost that is slightly acidic. Most gardeners will use the hydrangea as a companion plant to azalea or rhododendron. Both of these plants, likewise, prefer slightly acidic soil. The area selected should be well-drained, as standing water will quickly cause the roots to decay. Water daily as soon as the buds appear.

Hydrangea is sometimes considered a one-season “throwaway” plant, not literally to throw it away but to cut it back each season and allow it to regrow and bloom the next season.

Propagation of this plant can be made vegetatively by using stem cuttings. Cuttings made in June or July should be placed in a container of water. Within a few weeks the cutting will develop roots. Plant them in a mixture of light potting soil and sphagnum. The potted plant will make an ideal accessory for your windowsill or terrace. As the plant gets larger, either repot in a larger container or place it in your garden.

Pinching apical leaves above well-developed lower leaves will result in an abundance of flowers. The pinching process should continue until the end of July.

Cut the flower heads off the plant after it has finished flowering. If the plant is in a pot, move it to a warm, humid spot or plant it in the garden in a sunny, airy spot along with some acidic soil. If the plant is small enough, bring it indoors before the first frost. Cut it back to the lowest pair of buds and water sparingly until the first flower buds appear.

Major disease concerns are spider mites, aphids and mildew. Too little water will result in leaves that curl downward and turn brown. As a final note, forced hydrangea grown and purchased in a pot are generally not winter hardy. They must be bought indoors before the first frost. Hydrangea purchased as a burlap bush has been grown to withstand the winter and is capable of withstanding the vigors or fall and winter.

Plant Tips

In terms of keeping those nasty bugs away from you, a few drops of lavender oil behind your wrist, ankles and ears will repel most insects. It seems that insects don’t particularly care for the lavender scent. I do hope that your special someone is not repelled. Oh, well. Every solution has some downside.

Hardy Herb Gardens

Many gardeners love to plant herbs but are upset in replanting them each year. There are two solutions to this problem. A long list of perennial herbs is available, and they are hardy and will survive the most bitter winter. Among this grouping are chives, fennel, sage, tarragon, thymes and winter savory. A number of medicinal herbs will likewise bloom during the spring. They include arnica, catnip, Echinacea and feverfew.

A second solution is to plant species that are self-sowers, that is, they disperse their seeds so efficiently each year that you are almost always assured a second crop the following year. The key is not to harvest all the plants but to leave about a third of the crop to go to seed — they will do the rest.

Some self-sowers include borage, dill, chervil and coriander. They won’t necessarily come up right where you want them, but they will blend in with your other plantings and can be removed quite easily if they are really in the way.

Questions and concerns regarding gardening or plants care may be addressed by e-mail to Harvey.Goodman@att.net.

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