A hike along the Putah Creek Cold Canyon trail at this time of year may give you a glimpse of beautiful fall colored leaves from our Bigleaf Maple (Acer macrophyllum) where both the common and the scientific name hint at the size of its massive leaves which are the largest of any maple measuring nearly 12 inches (15-30cm) across. The trunk can be up to 3 feet in diameter (~1m) and it can grow up to 115 feet (35m) in height. As a moisture loving tree, it grows in sandy/loamy soils in moist canyons or bordering streams. It can be found predominantly adhering to drainages along the Pacific Coast from southern California to southern Alaska with a few isolated inland stands in mountainous regions in California and Idaho.
Commercially, this maple produces a good quality hardwood, but it is not typically harvested in California where it grows among other coastal tree species that have higher value. Native Americans used the fibrous inner bark to make baskets and clothing. Many parts of the tree are edible for humans including the inner bark, leaves, seeds and sap. Although the sugar content of the sap in the Bigleaf Maple rivals that of its relative the Sugar Maple (Acer saccharrhum), it has not been commercially tapped. It is a relatively fast growing tree and does have beautiful fall colors, but its large size and high water needs might not make it practical for use in water-conscious landscaping in the lower Putah Creek region.
The change in leaf color is caused when the tree begins to prepare for winter by shutting down the green chloroplasts associated with food production, a process called “senescence”. As the senescence process progresses, the chlorophyll begins to break down and the fading green color allows red and yellow colors to appear. If you are up for a nature hike and would like to see one of these trees for yourself, it may be easiest to find while it is producing fall colors (right about now) where it grows along the Cold Canyon trail below the Lake Berryessa dam.