Azaleas belong to the Rhododendron family, and grow with a variety of sizes, colors and blooming times. Growing conditions affect the color of azalea blooms. Many azaleas bloom with brighter colored flowers when they are planted in exposed areas rather than shade. Lower night temperatures and the soil pH also affect the color of azaleas. Azaleas go through a color change with age and get lighter with the years. To get your white azalea flowers to bloom blue flowers again, review the plant's growing conditions and soil.
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Use of Fast-Growing Methods
Azaleas are often subjected to fast-growth methods, which causes them to lose their color. Unless they are grown in a typical garden environment to their specifications, azaleas will not bloom in their natural color. These fast-growing methods include daily watering, an excess of liquid acid fertilizer and growing in plastic containers. Such an environment is foreign to azaleas and causes the darker colors to get light. For this reason pink or blue flowers turn white and red flowers turn orange and yellow.
Azaleas flower colors are sensitive to soil fertility as well. The plants require a high level of organic matter in their soil. If the soil has a high clay content, use a mixture of 50 percent ground pink bark or a leaf mold of oak or pine leaves, 25 percent of coarse sand and 25 percent of topsoil to amend the soil. Do not use too much peat, since this holds in excessive moisture during spring and winter. In soil that is naturally sandy, use a mixture of 50 percent organic matter and 50 percent soil to amend the soil.
Azaleas need an acidic soil for optimal blooms. The flowers react quickly to poor soil composition by fading in color. Azaleas thrive in a pH level between 5.0 and 5.5. If the soil is alkaline, add lime to increase the acidity. Amend overly acidic soils with organic matter in the top 6 inches and sulfur or ferrous sulfate. A lack of iron in the soil combined with an inappropriate pH also lowers the color-forming chlorophyll in the plants and may cause blue azaleas to fade.