In 2009 Holiday Island resident and Eureka Springs Independent reader, Leah Nelson, noticed an extraordinary leaf on a sidewalk in Rogers, Arkansas—a giant sycamore leaf that was 16 ½ inches wide, and 13 ½ in. long, more than twice the normal size. This fall at Black Bass Lake I found a small group of Sassafras trees with leaves that were far from normal. Usually Sassafras has three types of leaves— simple oval leaves, mitten-shaped leaves (with one prominent lobe), and three-lobed leaves. Sassafras leaves are “always” longer than wide. On these trees, a large percentage of leaves were 5-7-lobed, and up to three times as wide as long. Back in the early 80s I wrote about an Ozark Witch Hazel (Hamamelis vernalis) plant that I found that was brilliant scarlet red. It’s usually yellow to orange-tinged. A plant breeder in up-state New York saw my article and traveled to the Ozarks just to see the plant. He collected it, propagated it and offered it to his customers. These are examples of what horticultural breeders refer to as “sports”—variations from a plant’s “normal” morphological features. It’s all part of the package that nature delivers as endless variation.
It is this endless variation that horticulturists exploit to bring unusual or new plants to gardens. The famous plant breeder, Luther Burbank (1849-1926), gave us the giant Idaho potato (the Russett-Burbank potato). Before that one could hold a handful of potatos. Inspired by Charles Darwin’s 1868 book The Variation of Animals and Plants under Domestication, Burbank planted dozens of acres of daisies, then walked up and down the rows, selecting a handful of “sports” from which to collect seed for propagation. The rest of the field was plowed under. From those selections the Shasta daisy was born. These types of variations usually are not described in field guides. They are freaks of nature, genetic twists of fate, or perhaps some inexplicable response to the environment. Who knows! We just hope that when we find such mutations that they are not induced by man-made chemicals unleashed to the air, soil, and water or from genetically modified organisms. Let Nature work her own wonders.
This year fall colors came in waves. First a wave of glorious yellows and reds from Sugar Maples (Acer saccharum) planted around Eureka Springs, Arkansas. I couldn’t help but notice that the Sugar Maples planted along the sidewalk in front of the Best Western Eureka Inn at the top of Planer Hill showed their colors and dropped their leaves before the wild Sugar Maples in the forest directly across the street even began to turn color. Same for the Sugar Maples along Spring Street. Those planted along the street have dropped their yellow-orange leaves, while those in the adjacent woods have a glorious color display of orange to burgundy leaves, dominating the current color trend. So what is the difference between the colors and timing of the planted Sugar Maples and wild Sugar Maples? I suspect it is some type of genetic clock trigger. Which begs the question, how are autumn tree colors formed?
There is no single, definitive answer to the question of why trees turn color. Much of our understanding is physiological. The major factor among a myriad of variables is the diminishing length of the autumn day, hence the amount of daylight. Production of chlorophyll ceases, and as the green chlorophyll degrades, sugars and anthocyanadins (the vast group of compounds responsible for color combinations of fruits, leaves and flowers) begin to dominate the leaves, aided by the variables of moisture and temperature changes. The recipe changes from year to year and species to species. This is convention wisdom.
In the last 20 years an entirely new field of study—plant-animal interactions— hints of broader mechanisms, beyond mere physiological changes in the leaves. Fall colors are integrated in nature, signaling to fruit-loving animals and insects that fruits are ready for harvest, thus aid in seed dispersal. In some trees, the colors may send a signal to insect herbivores that feeding is over. The new science of autumn tree color suggests the process is a mix of defensive, seed-dispersing, signaling, and physiological functions all working in a symphonic display of intricate beauty. Our role in the process is simply to enjoy it.