Pioneer botanist William Bartram observed flame azalea in north Georgia in 1775 and described “this most celebrated species of azalea” as being “in general of the color of the finest red lead, orange and bright gold, as well as yellow and cream color; these various splendid colors are not only in separate plants but on branches on the same plant; and the clusters of the blossoms cover the shrubs in such incredible profusion of the hillsides that suddenly opening to view from dark shades, we are alarmed with apprehension of the hill being set on fire. This is certainly the most gay and brilliant shrub yet known.”
Former Western Carolina University botanist Jim Horton noted in The Summer Times (1979) that, “While most plants of the species produce orange flowers, variations all the way from lemon yellow to deep red can be found. One careful observer, Frank Miller of Waynesville, told me that some bushes produce darker flowers as the flowering season progresses, going from yellow to orange or from orange to red.”
The most likely explanation, in my opinion, for this light-to-dark color change probably has to do with insect attraction; that is, by displaying various shades of flowers over a period of time the plant has a better chance of attracting a more varied set of pollinators for cross-fertilization. Another example of this sort of strategy is the so-called “confederate” violet, which is simply a white-gray color morph of the common blue violet — a variation that allows the species to attract pollinators under varied light conditions.
As beautiful to our eyes as the flowers of flame azalea and all the other showy flowering plants are, they were not devised for our pleasure but to beguile pollinators in order to perpetuate the species in the most vigorous fashion possible.
Green, round, and spongy gall-like growths are often observed on the twigs of flame azalea. These are the result of a fungus that attacks the leaf buds.
At his Internet site (http://www.bio.georgiasouthern.edu/Bio-home/wolfe/ Wolfe.html), Georgia Southern University biologist Lorne M. Wolfe provides this information: “Along with Dr. Leslie Rissler (University of California, Berkeley) I have been addressing questions concerning the evolutionary ecology of disease caused by fungal pathogens. We have been working at the Mountain Lake Biological Station with Flame Azalea (Rhododendron calendulaceum), a native tree found in the forest understory in mountains of the southeast US. Prior to flowering the inflorescences that produce orange-yellow flowers are sometimes infected by large galls formed by a fungus. The Flame Azalea galls can attain the size of small apples and are formed by the fungus Exobasidium vaccinii, a disease common to members of the plant family Ericaeae. We are examining whether: 1) the presence of fungal galls has any effect on the growth and reproduction of the host Flame Azalea tree; 2) is there variation in the occurrence or intensity of disease among different populations, or between individuals within a single population? If there is variation in disease prevalence, then are there plant or population traits (eg: plant size, density) that may explain these patterns?
In his Wild Shrubs and Vines(1989), Donald Stokes provided additional information:
“The growths occur on the ends of the twigs and are about the size of a ping-pong ball.
They look a little like the green oak apple galls attached to oak leaves in spring, but instead of being stringy and tough, they are crisp, juicy, and sweet .... They were more well known in colonial times and were even pickled and stored for later eating.”