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Question: I had a blue hydrangea on the east side of my house, and last spring I moved it around to the west. It is pink around on that side of the house and I would like to know what to use to keep it blue.

Answer: The common French hydrangea depends for color on the presence of aluminum in the plant. In turn, the availability of this aluminum to the plant is directly influenced by the acidity of the soil. The soil on the east side of your house is more acid than on the west side. The soil may be acidified by the application of aluminum sulfate. Use about two ounces of aluminum sulfate to each square foot to be treated. Either scatter it on the surface dry or add it to water and sprinkle the area as soon as the frost is out of the ground. Other substances that may be used are alum, iron sulfate and sulfur dust.

Question: What should I add to my soil to have hydrangea keep its blue color? ED, Illinois

Answer: So long as the acidity or pH of the soil is kept at 5.5 or below the blue hydrangea will remain blue. The addition of aluminum sulfate to the soil early in the growing season will keep the soil acid. In April scatter about four to six ounces of aluminum sulfate around each plant or dissolve it in a pail, of water and pour it around the plant. If preferred, acidification may be accomplished by using sulfur dust or by adding iron sulfate.

Question: What can be done to make the flowers of my hydrangea turn white? Ours was loaded with flowers last year but they stayed green. The plant was taken from one that had snow white flowers.

Answer: It is the nature of the hydrangea (paniculata grandiflora) to bloom greenish white with the flower clusters gradually changing to pink and purple shades, and finally becoming almost brown. When they first bloom they should be nearly white. If the soil is neutral they seem to show a clearer white. Scattering a pound of hydrated lime around each plant in June may help the color of the flower clusters.

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Question: How long does it take a blue hydrangea bush to bloom? And how often should it receive aluminum sulfate? GB, Missouri.

Answer: Hydrangea hortensia is not a reliable bloomer in Missouri. except in the boot heel section of the state. The bloom buds winterkill unless the plant is given special protection. If the flower buds which are mature in the fall are not frozen during winter the shrub should bloom the first year after it is planted and each spring thereafter. As a rule it is advisable to grow the blue hydrangea in a tub anti store it in a root cellar or cool basement over winter. The flowers will be pink if the soil is alkaline and blue if the soil is acid. How much aluminum sulfate to apply, and how often, depends upon the soil in which the plant is growing, In general, when growth first starts, or at least by April, scatter a half pound of aluminum sulfate on a spare two feet square around the base of the shrub. An application once each year should he sufficient to keep the soil acid, Do not add lime to the soil or use fertilizer containing lime at any time.