In The News!!
Autumn Foliage: Nature paints with her own pigments
After a long, hot summer, many of us can’t wait for the approach of autumn and the promise of colorful fall foliage displays in our forests and landscapes. Have you ever wondered, though, what causes this amazing spectacle or how you can take advantage of this fall showcase in your own garden?
Nature’s Factories in Action
The mid-Atlantic region typically has outstanding autumn color. The shorter days and cooler temperatures signal the plants to begin a complex dance in an important group of chemicals within the leaves called plant pigments. These pigments color the plants like nature’s crayons in the fall.
So, how does this color change happen? Sunlight contains the complete spectrum of colors we see--red, orange, yellow, green, blue, and violet—as well as many we can’t see. During the growing season, plant pigments in the leaves capture the sun’s crucial light to make food. Different plant pigments team-up to absorb virtually all of the light with the exception of green, reflecting it back so plants appear green to the human eye. Leaves are typically green because of a group of pigments called chlorophyll.
With long days and warm temperatures, plants keep producing chlorophyll. However, as the days get shorter and nighttime temperatures become cooler, chlorophyll begins to break down. During this time, a group of yellow and orange plant pigments called carotenoids are gradually unmasked--having been hidden by chlorophyll throughout the growing season--revealing their stunning colors in autumn foliage. These pigments are also responsible for the orange color of carrots and citrus, as well as, the reddish-orange color of peppers and tomatoes.
Another group of plant pigments, anthocyanins, are responsible for red fall color. With the approach of autumn, biochemical changes in the plant signal the leaves to drop, trapping sugars in the leaves. These trapped sugars are used to manufacture the pigment anthocyanin. These red pigments act much like litmus paper (in much the same way as a hydrangea flower), producing better red fall color in leaves when soils are acidic and bluish-purple foliage colors when soils are more alkaline. The pH of the plant sap determines what shade of red or purple the leaves become. Additionally, red foliage color typically develops best in bright sunlight. Did you know that anthocyanins are also responsible for the red skin color in apples?
Unfortunately, not all plants produce colorful autumn displays, turning a disappointing dull brown color or dropping while still green. In some cases, leaves may contain high levels of plant pigments called tannins. During some years the fall color seems to be poor, with more brown foliage or early leaf drop. This is due, in large part, to the fact that the plant pigments responsible for good fall color breakdown prematurely and are overwhelmed by the brown tannins present in the leaves.
So, what weather is the best for the development of riotous fall color? Warm, sunny days, cool nights and dry conditions without a killing frost result in the longest and best fall foliage displays. Too much rain during late summer and autumn usually results in dull, muddy colors, while extended drought usually means there will be very little fall color. Weak color and a myriad of brown leaves this autumn might be attributable to our extended drought in late summer.
Bringing Fall Color into Your Garden
All of this science aside, what outstanding native plants can you incorporate into your own landscape to fulfill your autumnal cravings for color? One of the first native trees to develop shiny scarlet fall color in our region is black gum or tupelo (Nyssa sylvatica). Black gum is a large tree with an open graceful habit, equally happy in dry uplands, well-drained soils or a more moist backyard, as long as the soils are acid. Red maple (Acer rubrum) is a fast growing, large tree that will illuminate the fall landscape with dazzling orange and red autumn foliage. Red maple also likes acid soil, grows best in full sun, tolerating both wet and dry soil conditions. At Mt. Cuba Center, tulip poplars (Liriodendron tulipifera) are a fast growing tree that creates a cathedral-like feeling in the woodland landscape. In October, the landscape is painted golden with the yellow foliage of tulip poplar leaves reflected in the pond. Sourwood (Oxydendrum arboreum) is a medium-sized under-story tree for acid soils, offering a lovely burgundy autumn color with an upright irregular habit. Additionally, it produced clusters of white, lily of the valley-like flowers in mid-summer.
There are also a number of winning shrubs for the autumn landscape. Bottlebrush buckeye (Aesculus parviflora) is an adaptable large shrub with lovely spikes of white bottlebrush-like flowers in the summer (Butterflies love it!) and stunning clear lemon yellow palmate leaves in the autumn. Bottlebrush buckeye is a well-mannered shrub, ideal for a prominent spot in the landscape. Virginia Sweetspire (Itea virginica ‘Henry’s Garnet’), native in wet places throughout Delaware and New Jersey, is an outstanding shrub adapted to a wide range of garden situations. This arching shrub forms colonies and makes an outstanding informal hedge with fragrant, pendulous white flowers in June and July, turning a brilliant crimson color in the fall. Another fall shrub to covet for the garden is oakleaf hydrangea (Hydrangea quercifolia). This shade-tolerant shrub produces large white triangular clusters of flowers in mid-summer, remaining effective well into the fall. The oakleaf-shaped, large leaves of this plant develop a wonderful wine red color in autumn.
There’s no doubt that the forests of our region provide some of the best fall foliage color anywhere. Be sure to get out and enjoy the beauty of our native forests and get involved in protecting them for future generations. While you’re at it, consider purchasing some of the plants listed above to bring a little autumn color into your own backyard.
by Eileen Boyle
Education Coordinator
