Why Hydrangeas Are Different Colors!Posted by
Hydrangeas are fascinating in that, unlike most other plants,the can change color. Many wonder how this can be, a hydrangea planted in early ed colors three times by October.Many think it is in the pH of the soil by itself but William B. Miller, a professor of horticulture at Cornell ‘t agree.Hydrangeas are fascinating in that, unlike other plants, the colors of their flowers can change dramatically. Many think that the color change is due to pH levels in the soil, but “It is not the soil pH by itself but the availability of aluminum,” said William B. Miller, a professor of horticulture at Cornell University.
Aluminum is very common in the earth’s crust, but is available to the plant only in low-pH, or acidic, soils, Dr. Miller said. The plant absorbs the aluminum through the roots.
When aluminum gets up into the sepals, the colored segments that surround the tiny hydrangea flowers, it joins two other things that make the blossom blue: a pigment called delphinidin 3-monoglucoside and a co-pigment called 3-caffeoylquinic acid.
“Both are present in both blue and pink cultivars,” Dr. Miller said. If aluminum is available, he said, the blossom is blue, and if not, it ends up pink.
“Pink cultivars can be blue, and blues can be pink,” Dr. Miller said, and some can go both ways. But white cultivars, like Sister Therese, cannot become pink or blue.
As for a multicolored plant, Dr. Miller suggested two explanations: In limey soil, a plant that started out blue may make a partial transition to pink; or near new construction, where fill soil has been brought in, some roots may be in acidic soil, while five feet away, others are exposed to aluminum ions.
Photo credit: Austin Home Improvement Blog