Oak gallsAs the temperatures drop and the days become shorter the creek will start to show some of its impressive autumn colors. The vibrant, green shades of summer have already begun their transition to the yellows and reds of fall. These colors come from many sources, but the ones we’d like to highlight are the leaves and the galls.

It’s well known that fall brings yellow, orange and red leaves, but the cause of these colors isn’t always common knowledge. The green pigment in leaves is caused by the presence of chlorophyll, a pigment that helps plants absorb light energy and make food out of it. As the days grow shorter and there are less hours of daylight, the plants make less and less chlorophyll, eventually losing their green appearance. After the chlorophyll is gone another group of pigments start to show: carotenoids. Carotenoids are responsible for the orange colors in the leaves as well as the orange color of carrots! The red color in some leaves is caused by another chemical: anthocyanin. This chemical is only present in some plants and its use isn’t exactly known.

Leaves aren’t the only things bringing warm tones to the creek, galls are too! Galls are formed when certain wasps lay their eggs in the soft tissue of plants. These eggs cause the plant to grow around the egg, thus protecting it until it hatches. Many galls in our region don vibrant shades of red and orange, adding even more color to the already vibrant setting. The California Gall Wasp lays its eggs primarily in live oaks, which eventually develop into large, red, apple-like growths.

The shades of autumn are always a spectacular sight, but they won’t stay around forever. Once the leaves start to change color it’s a race against time to see them before they fall off for winter. November will be a great month to go out and see our creek transform as the seasons change.