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Species In Our Midst
Rhododendron minus

by Sally Perkins


Rhododendron minus var. minus Group Carolinianum
Picture by S & J Perkins
Rhododendron minus Group Carolinianum in Salem, NH


Rhododendron minus

Rhododendron minus is a lepidote (having scales) species in the Subgenus Rhododendron and a monotypic species in the Subsection Caroliniana. It is a variable species, native from the mountain tops to coastal plains of Tennessee, North and South Carolina, Georgia, Florida and Alabama along streams and rocky ridges. R. minus includes the now submerged names of R. carolinianum and R. chapmanii. Andre Michaux described the species in 1792 giving it the epithet minus meaning smaller, which may have referred to the size of its leaves compared to R. maximum.

Rhododendron minus is variable in height from 3 to 20 feet (1-6 m), rarely up to 30 feet (9 m), forming a compact to open straggly shrub. The branchlets are scaly and the dark to light green evergreen leaves are also quite variable in size 2 to 4.5 inches (5 to 12 cm) long by 0.75 to 2.5 inches (2 to 6.5 cm) wide. The leaves are most typically broadly elliptic to lanceolate with the upper surface more or less scaly and the lower surface densely scaly. The scales may almost touch each other or be up to their own diameter apart. The leaf tip may be acuminate (tapered to a sharp point), acute or obtuse, with a mucronate tip and the base obtuse. The leaf blade may be flat or curved inward.

The inflorescence is 4 to 12 flowered and is usually only terminal. The better horticultural forms will have terminal and axillary flower buds in the upper leaf nodes or have multiple buds at the terminal. The corolla is narrowly to openly funnel-shaped, deeply 5-lobed with a pale green to orange flare. The corolla is 2 to 4 cm long ranging in color from purplish pink, pink, white and rarely pale yellow. The small, irregularly 5-lobed calyx has sparse ciliate hairs. The ovary is scaly.

There are 2 recognized varieties: var. minus and var. chapmanii. R. minus var. minus grows on the exposed cliffs of mountains, in the piedmont, and along streams of North and South Carolina, Georgia and Alabama. It is typically a straggly tall shrub but good horticultural selections for habit, late bloom time and color have been made. I grow two such selections, M. L. Webb' and 'Piedmont'; both blooming late in June.

S. D. Coleman, a Georgia nurseryman, suggested that in the southern Chattahoochee River basin of Georgia and Alabama R. minus is distinct horticulturally and more attractive in flower than the type from North Carolina. The ARS has funded research into R. minus southern forms for their distinctive qualities. R. minus from the Chattahoochee region appears to be shorter, more compact and earlier blooming by two weeks than those from North Carolina. Flowers of the Chattahoochee R. minus often have yellow-orange flares while typical flowers of R. minus have green flares. The following selections from the wild have been made of these southern forms 'Kolomoki' light pink to white flowers with a golden flare. 'Fort Gaines' delicate pink. 'Rockford' deep pink, and 'Unity' vibrant pink.

R. minus var. minus Carolinianum Group had been described as a separate species by Rehder in 1912 to distinguish the more northerly mountain forms. Although in the extreme forms differing characteristics with lower elevation and southern plants can be found, they are inconsistent and unreliable. There exists a natural continuum of intermediates, therefore; the designation as a species was negated. The Carolinianum Group has openly funnel-shaped flowers, a shorter floral tube, ovate leaves, and a more compact growth habit. Horticulturally speaking R. minus Carolinianum Group is the easiest rhododendron species to grow in New England often seeding into moist stream banks and moss covered ground. It may have less heat tolerance. It has been used extensively by breeders for cold hardiness and sun tolerance. Named forms that are highly recommended are: the white 'Gable's form', and 'White Gem', the pink, 'Helen Cascio' and 'Fairhaven', and the pale yellow, 'Burn's Yellow'.

Chapman's rhododendron R. minus var. chapmanii is an endangered variety often given species status as R. chapmanii. There are only 3 known populations in the hot coastal plains of northern Florida. Geographically isolated from R. minus var. minus it grows on sands that have abundant organic matter and are well drained at the surface but with permanently saturated acid water just below the surface. It prefers light shade and can be found between the drier pine-turkey oak vegetation and the more moist titi (Cliftonia) bogs. R. minus var. chapmanii grows to 6 feet (2 m) tall, and is stoloniferous, resprouting easily when cut back. The leaves are smaller than var. minus, with a rounded leaf tip and more oval shape. The leaves are aromatic when crushed and the upper surface is distinctly rugose. There are reports of some variability in color forms in the wild. Breeding with R. minus var. chapmanii is thought to increase the heat tolerance of its offspring. In my garden var. chapmanii resents winter sun turning a crisp desiccated brown when so exposed which keeps the plant low growing in my zone 5 garden.

In the wild, R. minus var. chapmanii is the earliest flowering but when the extreme forms are grown side by side in my garden, R. minus Carolinianum Group is the earliest (about mid-May in Salem, NH). R. minus var. chapmanii is the next to bloom about 2 weeks later, followed by R. minus var. minus. This can result in a 6-8 week period of bloom in my garden from different selections of the same species!

Suffice it to say, that R. minus has been a cornerstone of lepidote breeding for hardy hybrids. The majority of the Eastern breeders used selections of R. minus Carolinianum Group with its compact, floriferous habit in clear white and pink forms. 'Epoch' the tetraploid form of R. minus Carolinianum Group and 'Achiever' a pink selection were extensively used by Delp in his breeding program. Delp's 'Angel Powder' is 'Epoch' x mucronulatum white form and is a particularly nice early white. Mehlquist, Nearing, Gable, Kehr, Knippenburg, Fetterhoff and Leach have used R. minus in its various horticultural forms to promote hardiness to sun, cold, and heat as well as drought. Kehr's hybrid 'Southland' is a beautiful salmon-pink compact plant the result of R. minus var. chapmanii crossed keiskei, prostrate form, and it seems to be reliably cold hardy to at least -10°F (-23°C).

'P.J.M.' a grex of the cross of R. minus Carolinianum Group with R. dauricum Sempervirens Group put the Mezitt family and Weston Nursery on the map for the best rhododendron for New England gardens. They have named selections of superior forms such as 'P.J.M. Regal' 'P.J.M. Victor' and 'P.J.M. Elite'. The bright pink 'Weston's Aglo' and 'Olga Mezitt' (both minus var. compactum x mucronulatum pink hybrids) as well as the 3/4 minus heritage of the white 'Molly Fordham' have established hardiness and spring color in the tough New England landscape.

R. minus grows readily from seed, and can even naturalize along stream banks and moist rich woods in New England. It also roots easily and passes that trait on to its offspring. Good selections and cultivars are frequently propagated in Plants-4-Members. Weston Nursery sells the species and many hybrids of it. The Rhododendron Species Foundation can also be a source of plants. Hardiness of the species varies with the selection from zone 4 to zone 6. Good soil drainage is the single most important cultural requirement for success and in sunny locations its fine texture can develop into a hedge. R. minus is truly a species every chapter member should have.

Sally Perkins, Salem, NH.


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