POUND RIDGE, N.Y. (AP) -- Some hydrangeas beguile us with color changes that keep us guessing. Others awe us by climbing 60 feet and more to consort with squirrels and orioles in the trees.
There are more than 100 species, so a gardener can experiment to his or her heart's content with different kinds. Everybody knows the beautiful big globes of pink, blue or white, but a few are veritable kaleidoscopes in a single season.
Hydrangeas come as small trees, too.
Not the least of their talents, particularly the climbers, is their tolerance of at least some shade. But at the seaside, hydrangeas thrive in full sun. You see them everywhere in beach gardens.
Hydrangeas do best in southern and central zones and are chancy farther north than Zone 5. In very cold areas, they're grown in containers and sheltered in the winter.
Beyond the familiar blue and the pink, some hydrangeas achieve their glory in full white. Much loved of these is oakleaf hydrangea (H. quercifolia), displaying pure white blooms as long as 15 inches in midsummer. These gradually turn pink, and later burgundy. This shrub has been hailed as possibly America's finest.
A Hydrangea serrata called Beni Gaku is offered by Wayside Gardens of Hodges, S.C. (800-845-1124) that morphs in nuances of white, pink, lilac and red, best for Zones 6-8, at $19.95 apiece and three for $54.
For a long time, people puzzled over what caused color changing in the big leaf variety (Hydrangea macrophylla), often called House hydrangea or French hydrangea. It looked like some kind of magic until scientists traced the phenomenon to the acidity or alkalinity of the soil, known as the pH factor.
In hydrangea culture, blue likes acidity while pink goes for alkalinity. To get blue you can treat the soil with aluminum sulfate, available at nurseries. Treatment with lime will favor pink.
The grapefruit size of the globes and their brilliant colors account, of course, for their popularity. The climbers, on the other hand, have small flowers called ''lacecaps'' from their looks and are rivaled only by ivy for growing in deep shade. They thus make excellent coverings in difficult places like the shady side of a wall.
In my country setting with many shade-casting trees, both bush and climbing hydrangeas have prospered. In this part of the Northeast, 50 miles north of New York City (between Zones 5 and 6), my plants have rarely suffered winter kill, and so I have not cut them way back or hilled or mulched them for protection.
Deer, however, have regularly nipped in wintertime at limbs of a gorgeous oakleaf that we treasure, but not enough to harm it seriously.
I'm particularly fond of two climbers of the Hydrangea petiolaris variety. One, planted many years ago, has climbed 50 feet up the bark of a towering Siberian elm. There are flowers at eye-level and lower, but my kick comes from using field glasses to spot the highest-dwelling lacecaps.
I placed the second plant in a patio along a partly shady wall of my house about 10 years ago. It has become a magnificent vine, needing yearly pruning to keep it within bounds. Two years ago I bought a third H. petiolaris and planted it at the side of a shed where there is bright sunshine in the morning and deep shade in the afternoon. It has taken hold, but it will be a while longer before I see whether it climbs up the shed. Climbers take time to establish themselves.
In our time-pressed era, the fastest way to have hydrangeas is to buy young plants from nurseries, but, once established, the plants can be propagated. One way is to dig up a mature clump in early spring, split it up with a shovel, and replant the divisions. Another is by layering. You scrape off a ring of bark from a low-lying limb and bury the exposed part. This will produce a new plant.
Some experts say the right time to prune big leaf hydrangeas is when the blooms are fading, not later on.
Buds for the next season are formed late in summer, so pruning then or in the fall will deprive you of potential flowers. Over time, in hardiness chancy areas, you can judge from your microclimate -- the special conditions of your own garden -- whether you need to cut stems to the ground over winter. Anyhow, if severe winters kill shoots, the roots of the plant will survive and produce healthy new shoots.
Hydrangea gets it name from the Greek ''hydro'' for water and ''aggeion'' for vessel, the combination believed to refer to cup shape rather than need of water, although the plants do require plenty of moisture.
EDITOR'S NOTE: George Bria retired from the AP in 1981 after 40 years that included coverage of World War II from Italy.
End advance for Thursday, May 17
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