In addition to being evergreen, these three species have short flower tubes and ten stamens. The shrubs native to North America that we know as azaleas (flame azalea, pinxter flower, pink-shell azalea, etc.) are also classified taxonomically as species in the Rhododendron genus, but they are deciduous, have long flower tubes, and display from five to seven stamens.
Please note that these characteristics apply to North American species only; in other parts of the world, there are rhododendrons that exhibit azalea-like characteristics and vice versa.
Rosebay rhododendron, the most common evergreen type in the eastern United States, grows as a straggly bush or small tree with long pointed leaves along low elevation stream banks and in woodlands into the higher elevations. It displays delicate white or pinkish-white flowers, with a peak blooming season occurring about mid-June.
Found only in the southern mountains from West Virginia to north Georgia, Catawba or purple rhododendron is considered by some to be the signature plant of the region. In regard to pure eye-catching masses of color, it is the showiest by far of the evergreen rhododendrons. Above 3,000 feet, it grows as a compact shrub, displaying shorter more rounded leaves than rosebay. It favors rocky slopes and ridges, as well as naturally treeless areas called heath balds. Peak flowering periods vary from year to year. Blossoms appear in some areas in late April and May. In mid-June at Craggy Gardens along the Blue Ridge Parkway just north of Asheville (milepost 364), the Catawba rhododendrons put on a floral display that attracts thousands of visitors.
Carolina rhododendron, the least common evergreen species, is something of a mystery. Various growth forms used to be classified as distinct species (R. carolinianum or R. punctatum), but these are presently lumped together as a single species (R. minus).
Also known as dwarf rhododendron, piedmont rhododendron, and deer-tongued laurel, Carolina rhododendron displays leaves that are very short, not much larger, in fact, than those of mountain laurel. It is native to the piedmont and mountain regions of the Carolinas, Georgia, Alabama, and Tennessee. The undersides of the leaves are rusty in appearance due to an accumulation of resin scales.
According to Arthur Stupka’s Trees, Shrubs, and Woody Vines of Great Smoky Mountains National Park (University of Tennessee Press, 1964), dwarf specimens that appear at elevations above 4,500 feet in the Smokies normally flower during late June and early July. At elevations below 2,500 or so feet, larger specimens of up to ten feet in height flower from mid-May into mid-June.
The blizzard of 1993 brought down a number of eastern hemlocks along the creek just above our home in Swain County. This created a sad mess, but it did open up a steep slope on the far side of the creek. We now have clear views of a number of Carolina rhododendrons of the taller type that were formerly hidden away from everyday observation.
In this instance, familiarity hasn’t bred contempt. Just the opposite. Carolina rhododendron has become my favorite of the evergreen rhododendrons. The entire shrub has a light, airy aspect that is in some ways more pleasing than the sometimes dense, cumbersome nature of its evergreen cousins. Less gaudy than Catawba rhododendron, the sparkling petals of the Carolina rhododendron light up the woodlands with ethereal colors that range from snow white to pinkish white to magneta.
This past weekend I conducted a natural history workshop for the North Carolina Arboretum along the Blue Ridge Parkway in the vicinity of the Pisgah Inn. If you want to view Carolina rhododendron in all its glory, now is the time to drive that section of the parkway. Be aware that the nearly leafless shrubs displaying incandescent pink flowers are pink-shell azalea (Rhododendron vaseyi). Right now, these two types of rhododendrons — one evergreen, the other deciduous — are putting on a display the likes of which I’ve not previously observed.