Colors in leaves come from pigments present in the leaf tissues. Chlorophyll is the pigment responsible for the green appearance of leaves, but other pigments are hiding inside beneath chlorophyll’s green mask. Cooler fall weather and shorter days tell plants that it’s time to cut back on chlorophyll production in preparation for winter. As the green pigments begin to break down, the other colors begin to show through. Yellow and orange colors come from pigments called carotenoids (note this word’s resemblance to “carrot”) which also give their colors to pumpkins, squash, daffodils and corn kernels. Another group of pigments, called anthocyanins, is responsible for intense reds and crimsons. These pigments form as sugars present in the leaf tissues break down.

Carotenoid levels remain fairly constant from year to year, so we don’t see much fluctuation in yellow intensities. But weather and temperature can greatly affect anthocyanins. A combination of warm, sunny days and dry cool nights produce the most spectacular displays of red and purple leaves. Warmth and sun activate a leaf’s remaining chlorophyll, causing it to produce large amounts of sugar. Cool nights cause the veins in the leaf to close down, preventing the sugar from moving into the rest of the plant. When large amounts of sugar get trapped in the leaf, they break down into anthocyanins and provide us with spectacular colors.

If you visit one of the peaks in Boulder’s mountain backdrop this month, you may come upon the annual ladybug spectacle: thousands of these insects migrate to the peaks, where they join swarms that cover rocks and trees. The ladybugs, properly known as “ lady bird beetles ,” are preparing to hibernate among rocky crevices and in dead trees. Hibernating in swarms may help the beetles conserve some body heat during the cold months.
 About 475 species of lady bird beetles occur in North America. They come in various shades of red, orange, yellow and even pink! Adults are oval-shaped and most are speckled with black markings.

Contrary to popular myth, you can’t tell a lady bird’s age by counting the spots: each species has a particular number of spots which remains constant through the beetle’s life.
 Most lady birds are ferocious predators. They eat small soft-bodied insect pests like aphids, mealy bugs, mites, and scale insects, chomping on scores in a given day. Scientists estimate that a single lady bird beetle may eat 5,000 aphids during its life! That’s a good friend to have in your garden.