By Steve Roark
Volunteer, Cumberland Gap National Historical Park

In mid to late summer if you’re out and about you will likely see plants bearing fruit going through color stages, especially blackberries right now. Blackberry and several other wild fruits go from green to red and finally black or blue when they fully ripen. As is almost everything in creation, there is a purpose to the color change.

Plants produce fruit that we and numerous animals enjoy eating, which is the point of making fruit. They want their seeds to get dispersed and are willing to bride wildlife to get it done. The animal eats the fruit for the tasty flesh and swallows the inner seeds as well and may walk or fly some distance from the mother plant. The hard seeds pass through the animal's gut undigested, and when the animal eventually poops, deposits the seeds with fertilizer to boot.

To ensure that they are seen for consumption, many fruiting plants display what is called "pre-ripening fruit flags", going through the series of color changes as they ripen. Raspberry, cherry, mulberry, blackberries, blueberry, all start out green, and as they mature turn pink, to red, then purple, black, or blue when fully ripe. This color change serves as a signal to animals that fruit is about to ripen, encouraging them to stay in the area to feed. This ups the chances of getting the seeds dispersed.

Another trick some fruiting plants use is to go through a very early leaf color change in the fall. The bright red or yellow leaves are very distinct against a predominantly green background and are thus attractive to animals (especially flying birds) from a distance. This early flush of color is called "foliar fruit flags", and is used by Poison Ivy, Virginia Creeper, Sassafras, Blackgum, Wild Grapes, Dogwood, and Spice Bush to announce ripe or near ripe fruit.

Black Bears in particular make use of the ripening color signal. They are voracious eaters, especially late summer and fall, to accumulate enough fat for hibernation. They will stay in an area eating the same fruit for days until it is gone. This excessive eating habit is called hyperphagia, so again there is a purpose for simple things in nature.

The next time you enjoy wild fruit of some kind, keep in mind you are being conned, but that’s okay because both sides win.