I have read several postings regarding a color change in Hibiscus. Someone mentioned it might be a "scientific thing". And, you would be right! I took a Science of Plant Color class a couple semesters ago and this is what I remember about plant pigments.....it might help explain the color change a little.

Sounds to me as if the weather is playing a part in your color changes. That is the fascinating thing about Hibiscus. They will change color given a temperature change.

Why? Well they contain three compounds: Carotenoids, Favenoids, and Anthocyanins. These are the pigment compounds. These compounds respond differently to light and temperature. All plants contain some level of these compounds.

So....brief explanation regarding the pigments and changes in your Hibiscus.

Hotter weather and more light will increase carotenoids in the plant. Carotenoids are responsible for the red, orange spectrum. So a little bit of carotenoids will create a yellow color. As the content of carotenoids increase the flowers will increasingly become orange and then red with high levels of carotenoids. These are the most stable of all three compounds and will hold their color the best. Think of the carotenoids as the same for a tomato....it starts out green in color....but as the days grow longer and the heat increases the tomato will turn red.

Anthocyanins are responsible for the blue, purple, pink, red and black spectrum. They have the a slightly different effect of carotenoids. In colder temperatures they will increase turn off and cause a plant to turn red. In heat they will degrade and cause the plant to change color into a faded color along its spectrum. Another way to relate this is with trees. As the days get colder the plant's chlorophyll content is lowered (we all know it is responsible for green colors in plants). So, as the chlorophyll decreases, the anthocyanins increase and thus the leaves turn red, orange, etc.

Flavenoids are responsible for the pale yellows and white coloration of a Hibiscus. They act much like an anthocyanin in the colder weather and lots of light will cause an increase in the pigment and change the coloration to yellow. In heat they will degrade and cause a color change to white. Some plants, such as the hosta will contain higher levels of the flavenoids. You can see their variegated coloration such as white and green. The white coloration protects the plant from UV light and thus protects the plant from cellular death.

Plants are amazing specimens. Coloration is dependent on environment, temperature, light, some respond different to Nitrogen (Hydrangea) and some are a specific color to protect it from UV light and/or predators.

So, there you go....for anyone who ever wondered "Why did my Hibiscus change color?" This is the best explanation I have.