During a narrow window of time in fall, the simple transition of lush green leaves to showy brilliant primary colored specimens has many faces turned up in wonder. The autumnal changes of color in our local flora are a sight to behold and appreciate- and they provide a simple lesson in the science behind the phenomenon and our native plants that star in the show.
We all know from our elementary science that plants are their own miracle factory of food production. They take up sunlight, water, and carbon dioxide and through an amazing process called photosynthesis, they form their own food. Crucial to this process is chlorophyll, also the chemical that gives the leaves their bright green hue.
The shortened hours of sunlight during fall days prompts plants to slow, and eventually stop this food making effort. As this happens, the green chlorophyll slowly departs from the leaves, allowing us to see what lies beneath.
The first stars in the show are carotenoids and anthocyanins. These produce yellow, orange, and brown colors in the leaf. Often, these substances have been present all along, yet have simply been covered up during the growing season. In fall, they step from behind the curtain of chlorophyll to show the warm colors within.
In addition, glucose and surplus materials in the leaf are often trapped behind as the nutrients of the plant are drawn back into the main parts of the plant. These remants can provide the greatest show with reds, burgundies, and purples gracing the once emerald palette.
The greatest places to view this show of colors are often the habitats occupied by our own native plants. Here we provide our favorite species for beautiful fall viewing (Plants of the Rocky Mountains, 1998):
Narrowleaf cottonwood (Populus angustifolia): found growing along rivers and streams from the foothills to the montane zone. Autumn leaves of bright yellow, lanced shaped and long.
Quaking aspen (Populus tremuloides): Found growing in dry to moist sites, from the foothills to the subalpine. Autumn leaves of gold on long stalks that tremble in light breezes.
Red osier dogwood (Cornus stolonifera): Found growing in moist wooded to open sites from the plains to the montane. Autumn leaves of crimson or red, closely matching the red tinged branches.
Mallow Ninebark (Physocarpous malvaceus): Found in dry, open, or lightly wooded slopes of the montane. Autumn leaves of orange to red, somewhat maple-like.
Chokecherry (Prunus virginiana): Found dry to moist open sites from the plains to montane. Autumn leaves of crimson to purple, oval shaped and pointed at tip.
Take the time to get out and enjoy this show of nature’s free handiwork, and appreciate native plants for yet another service they provide.