It’s peak fall color in southwestern Pennsylvania, depending on who you ask! This beautiful specimen of red maple (Acer rubrum) was collected on November 2, 2007 by Loree Speedy near Virgin Run Lake in Fayette county. It is unclear to me what exactly the “red” in red maple refers to specifically, or perhaps many parts of the plant (flowers, leaves, petioles). One thing is for sure – it can have beautiful bright red foliage in the fall. Also once called “swamp maple,” this species is widespread across eastern North America. Due to altered effects on fire, wildlife management, climate, and other environmental changes, red maple is said to have increased in abundance over the past century.
Red colors can be the most striking of all fall colors…but my opinion changes! This specimen shows great variation within the leaf, with reds and greens. Each leaf have a certain uniqueness to them.
Red coloration in fall leaves results from the production of red pigments called anthocyanins. The pigments serve as a protectant, a sunscreen of sorts. You may also see young or stressed leaves turn red at other times of the year for similar reasons. Other pigments like carotenoids (oranges) and xanthophyll (yellows) are present throughout the growing season, serving as accessory pigments for photosynthesis. As chlorophyll breaks down and nutrients resorbed, these colors have their chance to shine. Anthocyanins, however, are actively produced in fall.
Fall leaf coloration is complex, and not easy to predict. Many hues exist, even within a leaf (as shown in this specimen). Every species has different coloration. And, coloration differs within species based on a variety of factors. Each leaf is unique and although short, fall is a great time to celebrate the beauty and science of leaves.
All of the red maple specimens in the Mid-Atlantic region from the Carnegie Museum herbarium are now imaged and available online.
Check back for more! Botanists at the Carnegie Museum of Natural History share digital specimens from the herbarium on dates they were collected. They are in the midst of a three-year project to digitize nearly 190,000 plant specimens collected in the region, making images and other data publicly available online. This effort is part of the Mid-Atlantic Megalopolis Project (mamdigitization.org), a network of thirteen herbaria spanning the densely populated urban corridor from Washington, D.C. to New York City to achieve a greater understanding of our urban areas, including the unique industrial and environmental history of the greater Pittsburgh region. This project is made possible by the National Science Foundation under grant no. 1801022.
Mason Heberling is Assistant Curator of Botany at the Carnegie Museum of Natural History. Museum employees are encouraged to blog about their unique experiences and knowledge gained from working at the museum.