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There are some 500 varieties of Hydrangea macrophylla in the world. The flower has two kinds of blossom: very small ones (which are the actual flowers) and others with large, colorful petals and sepals. In general, the flower is large and semi-spherical, and stands out clearly against the dark green of the leaves.

Planting
In spring or autumn, never at times of cold weather.� Make a hole twice as big as the dirt ball of the plant and water it abundantly. If the soil is not acidic, dig a much bigger hole and fill it with heather or chestnut.

Care
Hortensias need share, or semi-shade, a lot of water and protection from the wind. Under a tree is a good place because the tree filters the light, as is a sheltered spot by a wall facing north.

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The flowers' blue color does not come from iron in the soil, but rather the existence of free aluminum that they can absorb from acidic soil.

There are two ways to make pink hortensias turn blue: sprinkle aluminum sulphate around the plants, or when you water them add a bluing agent of the kind sold in garden supply stores. White hortensias don't change color.

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In general, hortensias should not be pruned in spring or after they bloom because this way you lose a lot of flowers. Depending on the variety of plant, pruning is done at some point in winter, keeping in mind that the flowers will bloom in the following season from the young shoots which sprouted the previous year.

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To start new hortensias, collect semiligneous cuttings at the end of summer and in the autumn.

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Interesting hortensias
There are climbing hortensias such as the Hydrangea petiolaris, which can grow to 18 meters in length. They cling to the wall with small roots like those of ivy. This hortensia has white flowers all around the plant and does not need to be pruned. It does need shade, however.

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The Hydrangea serrata, is smaller and the flowers are flattish. They have large pink petals on the outside and whitish flowers in the center that start off white, then turn pink and finally purplish as the flower matures.

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Hydrangea quercifolia has huge leaves like those of oak trees and white flowers in bunches. They take on a beautiful color in autumn.