Why do autumn leaves change colour?
by Nancy Melcher
With autumn well upon us, it’s time to dust off the rakes, stock up on leaf bags, and make appointments with the chiropractor. All the lovely leaves that have provided us with summer shade are about to drop. But before they blanket the ground, they delight us with an incredible display of colour: multiple hues of vibrant red, sunny yellow, and sunset orange! Why do the leaves change colour in the autumn?
The green colour we see in the leaves in spring and summer comes from chlorophyll, the food-producing pigment that converts sunlight into food for the plant. In the autumn food production slows due to fewer hours of sunlight and cooler temperatures. The green fades away: what remains (those amazing blazes of fiery colour) has been there all along, but hidden by all the green.
The intensity of the colours depends on a few things. Temperature, the amount of sunlight, and soil moisture in the growing season all contribute. Clear sunny days allow good pigment production. Plenty of moisture in the soil, and warm temperatures, mean good leaf growth. Now, cool crisp nights help keep the colours bright longer. Heavy rains and strong winds can blow the leaves off the trees before they can reach peak colour.
Plan to get out for a walk on one of the many trails in and around Uxbridge in the next few weeks. Enjoy the brilliant displays that the fields and forests will provide as they prepare for the chilly winter weather that’s next on the nature schedule!
Nancy Melcher is The Nature Nut. Send details of your sightings or questions about the natural world to: firstname.lastname@example.org.