Bushes With Blooms That Change Color

Soil pH Levels

• The soil, whether naturally in the ground or purchased potting soil, has a pH level. The pH is how acidic or alkaline the soil is, and that measurement affects the growth and color of plants. Many plants require a certain pH level to grow properly, and some plants die if the pH level is too low or high. The level changes based on the amount of nutrients--including aluminum, potassium, nitrogen and phosphorus--in the soil. The change in pH levels affects the colors of flowers, especially the hydrangea.

Hydrangea

• The hydrangea is a large shrub with giant flowers that look like large balls of petals. The flowers vary from blue to purple, from pink to red and plain white. The pigments in the plant determine its color, and if no pigment is available, the plant is white. In order to change the color of the hydrangea, it must have pigment; therefore, white hydrangeas will not change color. It is possible to see one hydrangea bush with both blue and red flowers. It all depends on the amount of aluminum the flowers receive, and that amount affects the pH level of the soil. Use the pH level as a measurement to determine if the soil has the right amount of aluminum to change the flower color.

Changing the pH

• It is possible to change the hydrangea flower color from pink to blue, or vice versa by adjusting the levels of aluminum in the soil. When there is little aluminum in the soil--creating a high pH--the flowers become pink. When there is a lot of aluminum--which lowers the pH--the flowers become blue. To remove aluminum from the soil, add lime and phosphorus to the soil. Both raise the pH and stop aluminum from forming. To add aluminum to the soil, mix aluminum sulfate in the soil until it reaches a pH of 5.2 to 5.5. At that pH level, the soil should have enough aluminum to change the color, but not so much that it kills the plant. Growing the hydrangea in a pot helps to control the soil, as it is a smaller area. However, please note that the process is not foolproof, and the flower may not change color.

Alternatives

• Besides the hydrangea, a few other flowering bushes change color due to pH levels. The morning glory bush, and all morning glory plants, change color from the morning to the night. In the morning, the unopened buds of the morning glory are pink, but when they open in the evening, they are blue. Another example is yesterday-today-tomorrow, also known as the kiss-me-quick. The name comes from the fact that the flower blooms for three days, and on each day, it is a different color. It changes from violet to light pink and then to white. According to the United States National Arboretum, scientists are developing ways to change the colors of flowers by mixing pigments from one flower with another and changing the pH levels of the soil.