Growing Hydrangeas

Tips for the care and cultivation of hydrangeas.

Hydrangeas are hardy shrubs that thrive under most conditions. They can fill up awkward gaps in your garden, giving welcome color and texture during the late spring and summer months. If you prune them back in the winter they remain unobtrusive during those months when you would rather not have large, wet, unproductive bushes on show. And they have the unusual characteristic of having the ability to bloom in more than one color, depending on the soil conditions.

There are three main types of hydrangea, and their flower heads are the main differing characteristic. Mopheads are the common type, found in many gardens. They are what most people think of when they think of hydrangeas. Mopheads have large, round heads of compact blooms. The flower head varies in size between three and twelve inches, however is usually found in the middle of this range. Lacecaps are flatter than mopheads. Lacier blossoms surround a cluster of flowers in the center of the flower head. The third type is called panicles and is considerably less well known. They can either be long and pointed, or similar in appearance to a mophead. They will usually flower for very long periods and will tolerate a lot of sun.

As mentioned above, hydrangeas can be encouraged to bloom in different colors, with one or two exceptions. White hydrangeas will not change their colors, no matter what you add to the soil. Not all varieties of pink hydrangeas are amenable to color-changing tactics, either. Check with your nursery when ordering them, if this is important to you.

Hydrangea colors range from very deep pink to very deep blue. The following techniques will not affect the intensity of the color, only the actual color. Intensity of color depends on the characteristics of the plant stock, the weather, and the general health of the plant. Regular fertilizing will probably deepen the intensity of the color.

In general, hydrangeas are pink in alkaline soil, and blue in acid soil. If your soil condition suits the color you want, there is no need to do anything except fertilize and prune. To change the colors, you will need to change the pH balance of your soil, four to six months before the blooming season (i.e. at the end of the previous season).

Turn acid soil into alkaline soil by adding dolomitic lime. 3-8 cups sprinkled around the base of a large hydrangea, two or three times over the non-flowering season, should produce results by the summer. More lime will not damage the plant. Too little lime will not turn the flowers pink.



Turn alkaline soil into acid soil by adding aluminium sulfate. Use 3-4 tablespoons in a gallon of water, and apply twice, a fortnight apart.

It is quite likely that in the following season you will find a mixture of colors on your shrub. This can look extremely attractive.

Hydrangeas generally need modest, regular pruning. It is possible to leave them unpruned, and so long as they receive water and fertilization they will continue to flower, but they will become straggly and shapeless. Deadhead the spent blooms, as they look very untidy during the winter months. Young shrubs do not need much more than this, plus the removal of any obviously dead material. Older shrubs may have one-third of their oldest wood pruned during a mild winter spell. This encourages a pleasing shape, and allows light and air into the center of the shrub.

If your plant appears to be dead, try some severe pruning. Cut it back to a height of 1.5 meters from the ground, feed and water well. If you are lucky, new growth will sprout from the center of the plant. It will not flower in the current season, but if well cared for should flower vigorously the following year. They are robust plants after the first couple of years and will tolerate this rough treatment if necessary.

Hydrangeas need plenty of water. The plant itself will survive lack of water, and will show glossy leaves, but the blossoms will be few and far between. They also thrive on fertilizer. Homemade compost or mulch is ideal for hydrangeas, or a multi-purpose fertilizer applied in spring and autumn.

Most gardeners use hydrangeas to fill in gaps in garden beds, along fences and the like. They fit in well with the average planting arrangement and can look stunning in both large and small gardens. However in some parts of the world, such as the tropical islands of Madeira and the Azores, they are used as hedges on farms. I doubt if they are ever pruned, or fertilized beyond the odd cattle or sheep dropping, but they thrive in an untidy way and make remarkably beautiful hedges. It is something to be born in mind if you live in the tropics.

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