Anyone who has been in the vicinity of Clingmans Dome recently can tell you that the bright red American mountain-ash berries are out of this world right now. There are so many clumps of berries that the trees’ branches can barely support them.
Such an abundance of berries is a great opportunity for photographers, as well as an important food source for bear, ruffed grouse, squirrels, deer, cedar waxwing, and other types of native wildlife.
Yet this is the first time in at least three years that mountain-ash trees have put out a bumper crop in the Smokies. Why? For trees, berries serve an obvious purpose—to spread their seeds. Trees can’t move or toss their seeds very far, but bears and birds can. By producing seeds covered with brightly colored, nutritious berries, the trees attract animals that eat the berries, move to a location some distance away, and excrete the seeds along with a bit of organic fertilizer. If the excretion falls in the right habitat, an American mountain-ash seedling may sprout the following spring.
So why not produce seeds every year? It could be that a late frost killed the flowers so they didn’t turn into fruit. Or it could be a complex strategy for survival. According to park botanist Janet Rock, it takes a lot of energy for a tree to produce buckets of fruit each year, so doing so only every two or three years could allow the tree to dedicate more resources to growing branches, leaves, or roots. And maybe by putting on a really big, splashy berry display, it causes the birds and bears to finally take notice of the mountain ashes and focus their feeding on the berries. After all, if the bears and birds find a place with lots and lots of food, especially in the fall when they really need it, why move elsewhere?
Other trees in the Smokies seem to follow a similar, mysterious boom or bust cycle. Fraser firs, for example, don’t have cones this year, but may have a cone bonanza in 2017. And rosebay rhododendron can have stupendous super bloom years, but only every 2-4 years.