R. cumberlandense is the accepted name for the species that was formerly know as R. bakeri. R. cumberlandense is diploid,
but very similar in many respects to the tetraploid species R. calendulaceum. Since most if us are not able to discern
ploidy levels while hiking on the trail, we usually use a hand lens to look at the sepals and pedicels of the blossoms.
R. calendulaceum will have glandular sepals and pedicels whereas cumberlandense will be eglandular.
Although cumberlandense does tend to bloom later than calendulaceum, there are late blooming forms of calendulaceum
that will be in flower at the same time as cumberlandense at the same elevation. As for flower color, cumberlandense
tends more toward the orange-red shades in the wild, but we do see orange and gold forms and some approaching yellow.
I will say that I haven't seen any pure yellows cumberlandense plants in the wild as nice as image from Robert Day
shown on your site but that doesn't mean they don't exist. The problem we have with many native azalea populations
is that other species are often growing nearby so there is a tendency for the azaleas to hybridize. The hybrid swarm
on Gregory Bald is world famous, and there are four species suspected growing in that area. R. cumberlandense does
predominate so most of the plants will have orange-red to red flowers, but there is also arborescens, viscosum, and
calendulaceum very nearby and they produce flowers in wide range of colors.
R. calendulaceum does come in clear yellow, orange, and red, too. It is hard to quantify, but from an artist's eye,
the colors found in R. cumberlandense do seem more vibrant to me, a clarity and brilliance that generally surpasses
calendulaceum. Both are stunning native azaleas, though. R. calendulaceum tends to have larger blossoms, too, but
both species put on a great show. An isolated population of cumberlandense occours in the wild in the mountains of
Eastern Tennessee near the Cherohala Skyway not far from Tellico Plains.
There are a number of azaleas on Gregory with lovely clear yellow flowers, as fine as Robert Day's pictures, but I
wouldn't be so bold to say that any plant from Gregory is a pure species of one form or another. With all the
crossing and back crossing that has happened over the past centuries up there, I would suggest that most of the
plants are likely complex natural hybrids by now. The research by Dr. Tom Ranney and his graduates students
indicates that the majority of the Gregory Bald azaleas are probably hybrids between R. cumberlandense and arborescens.
Many of the azaleas on Gregory Bald are delightfully fragrant and since neither calendulaceum nor cumberlandense
are fragrant, the "sniff test" is another tool for identifying hybrids.