With autumn in full swing and cool, rainy weather beginning, we are blessed to see the transformation of foliage from spring greens to sun kissed yellow to deep oranges and reds. Some of the most colorful and vibrant autumn leaves comes from the bigleaf maples (Acer macrophyllum). Found in parks, backyards and even sidewalks, chances are, you have enjoyed their shade and crunched through their leaves this autumn.
The Bay Area, and California in general, is not known for fall foliage, but while our autumn colors might not rival those on the East Coast, don’t tell that to the bigleaf maples. With largest leaves of any maple, this deciduous tree goes through the beautiful cyclical transformation right here in the Bay. The cycle begins with green leaves growing in the spring and summer, thanks to the abundance of the pigment chlorophyll in the chloroplast, capturing the sun’s energy to utilize in the production of the plants “food” to nourish the tree.
As the days grow shorter and temperatures grow chillier, the chlorophyll levels decreases, allowing other pigments to shine through. Carotenoid pigments are unmasked (high green chlorophyll levels mask other pigments always present in the leaves) and vibrant shades of yellow, orange and brown burst into view. Red coloration from anthocyanin pigments also come into view, but they are new arrivals to the leaves, and have just been developed during the late summer thanks to the breakdown of sugars of the sap of the leaves and the reduction of phosphate levels. The bright colors of the bigleaf maple do not last on the branches. As anyone who has enjoyed an autumn walk through the woods can tell you, these leaves soon fall off the trees and cover the ground with a carpet of reds, yellows, oranges and browns.
The bigleaf maple is native to the Pacific coast of North America, all the way from southern Alaska down to southern California, including many parts of the Bay Area. These maples grow quickly, and can grow to heights of over 75 feet, although it is more common for them to stay around 30 feet. With large leaves and tall trunks, bigleaf maples often provide shade in parks. While it is possible to harvest maple syrup from the sap of bigleaf maples, it is uncommon, and usually the tasty pancake topper is harvested from the Sugar Maple, which boasts a higher sugar content (hence the name).
As November comes to a close, many of the bigleaf maples, and other deciduous trees, have lost many of their leaves. Enjoy them during this short window of bright colors and crisp weather; they are the perfect excuse to explore your local watershed and be in awe of the beauty of the natural world.