The emerging autumn in California colors

The air is crisp! Sweaters are in! Leaves are changing! Fall is in full swing!

While out on a pumpkin spice latte run, you may have noticed the lovely color changes in the tree leaves on your way. Many of us may wonder why certain trees alter and ultimately shed their leaves at the turn of the season.

Orange Sycamore leaves under a blue sky. Photo credit Justine Belson / USFWS

In short, this is a plant’s way of preparing for winter. Similar to how we unearth our charming winter sweaters at the first whiff of cold fall air, the trees change into their winter outfits too.

Many plants have soft, tender leaves that would freeze in the cold winter months. Deciduous plants undergo an annual process of discarding their leaves to avoid this. The leaf color changes we see in autumn are characteristic of those deciduous plants. 

The Don Edwards SF Bay NWR has many deciduous plants to learn from. Next time you are out on the trail, try using the iNaturalist App to photograph and identify deciduous plants.

Leaf color is determined by naturally occurring chemicals called pigments that produce specific colors. Chlorophyll is a green pigment common in most plants as it is an essential part of photosynthesis. When we think of plants, we often picture the color green from chlorophyll. However, when the fall season sweeps in, some plants begin to show other colors that were shrouded by chlorophyll the rest of the year. 

Leaf transformation occurs when the trees begin to sense the shorter days of autumn. The hours of sunlight are seasonally consistent, therefore making them a more reliable signal for plants than temperature or rainfall each year. In response to the detection of short sunlight hours, plants stop producing new chlorophyll. The old chlorophyll begins to break down and unmasks the other pigments that may have been there all along. This often includes carotenoids, which display a yellow and orange hue, xanthophyll for bright yellow, and anthocyanin for red. 

Of course, we also see plants that stay green and keep their leaves all year. These plants are appropriately termed evergreens. They often have waxy, small leaves that are tough enough to survive extreme weather conditions. Although evergreens are admired for their perseverance, they do not always bring that autumn flare that many desire in their streets and gardens. Below this article is a table outlining a short list of California native plants that can spruce up a garden, especially in the autumn. 

In addition to their beauty, California natives benefit the local environment. Having adapted to the region’s climate, these plants will not need as much care and maintenance as non-native plants would. They have specifically evolved characteristics that complement our weather, so they will not need as much water, pruning, lighting changes, etc. This saves water, and the local pollinators love having those native plants around! Many of our native plants have favorite visitors who feed on their flowers. Attracting and supporting local pollinators will help your garden flourish. In turn, you benefit from a luscious, low-maintenance garden with gorgeous fall colors. You may even kindle a new sentimental connection to your state by inviting California native plants to your home and learning more about them.

So, have yourself a lovely fall season and enjoy the fantastic display of emerging autumn pigments!

To learn more about California’s native plants and the wildlife they support check out https://calscape.org. To watch a great video explaining the science behind Fall colors: https://www.scientificamerican.com/video/why-do-autumn-leaves-change-col....