Hydrangea radiata
Encyclopedia
Hydrangea radiata is an attractive, deciduous shrub up to 3 m tall; its natural range is limited to the southern Appalachians
, where it is fairly common. Its common names—Silverleaf or Snowy Hydrangea—reflect its distinctive foliage which is dark green on top and silvery white below; the sharply contrasting foliar colors makes this shrub conspicuous at a distance, especially in a breeze.
from southeast Tennessee
, east to North Carolina
and northwestern South Carolina
, and south to northeastern Georgia
. It typically occurs near streams, rocky outcrops, and along roads, especially in the headwaters of the Chattooga River
and also in the French Broad River
Valley. It is conspicuous along roadsides near the junction of North Carolina, South Carolina, and Georgia—in the vicinity of Highlands, Cashiers, and Rosman, North Carolina
. Some outlier occurrences of silverleaf hydrangea have been locally observed in the Piedmont Region
; these populations may have escaped from cultivation.
) and ashy hydrangea (Hydrangea cinerea
). At one time both silverleaf hydrangea and ashy hydrangea were considered subspecies of smooth hydrangea. However, most taxonomists now consider them to be separate species, and that usage is adopted here. Evidence for separating these three closely related, native hydrangeas is based largely on cross-pollination experiments conducted by Ronald Pilatowski. The crosses yielded few viable seeds at best, indicating that despite overlapping ranges and characteristics, the plants maintained their genetic
purity and their unique phenotypic
characteristics.
The leaves of silverleaf hydrangea are large (8 to 15 cm long), opposite, serrated, ovate
, and deciduous
. The upper leaf surface has hairs along the veins. The lower leaf surface is densely covered with felt-like hairs, appearing bright white or silver; when viewed under magnification, these hairs are without tubercles (ashy hydrangea has numerous tubercles). These hairs are so thick that the lower surface of the leaf 's epidermis
cannot be seen.
s 4 to 9, although highly protected locations would be advisable in areas warmer than zone 6. Several popular cultivars are available (Samantha and Terri Greer).
Appalachian Mountains
The Appalachian Mountains #Whether the stressed vowel is or ,#Whether the "ch" is pronounced as a fricative or an affricate , and#Whether the final vowel is the monophthong or the diphthong .), often called the Appalachians, are a system of mountains in eastern North America. The Appalachians...
, where it is fairly common. Its common names—Silverleaf or Snowy Hydrangea—reflect its distinctive foliage which is dark green on top and silvery white below; the sharply contrasting foliar colors makes this shrub conspicuous at a distance, especially in a breeze.
Range/Habitat
Silver hydrangea is native to the mountainous region (usually above 2,000 feet elevation) represented by the southern Blue Ridge MountainsBlue Ridge Mountains
The Blue Ridge Mountains are a physiographic province of the larger Appalachian Mountains range. This province consists of northern and southern physiographic regions, which divide near the Roanoke River gap. The mountain range is located in the eastern United States, starting at its southern-most...
from southeast Tennessee
Tennessee
Tennessee is a U.S. state located in the Southeastern United States. It has a population of 6,346,105, making it the nation's 17th-largest state by population, and covers , making it the 36th-largest by total land area...
, east to North Carolina
North Carolina
North Carolina is a state located in the southeastern United States. The state borders South Carolina and Georgia to the south, Tennessee to the west and Virginia to the north. North Carolina contains 100 counties. Its capital is Raleigh, and its largest city is Charlotte...
and northwestern South Carolina
South Carolina
South Carolina is a state in the Deep South of the United States that borders Georgia to the south, North Carolina to the north, and the Atlantic Ocean to the east. Originally part of the Province of Carolina, the Province of South Carolina was one of the 13 colonies that declared independence...
, and south to northeastern Georgia
Georgia (U.S. state)
Georgia is a state located in the southeastern United States. It was established in 1732, the last of the original Thirteen Colonies. The state is named after King George II of Great Britain. Georgia was the fourth state to ratify the United States Constitution, on January 2, 1788...
. It typically occurs near streams, rocky outcrops, and along roads, especially in the headwaters of the Chattooga River
Chattooga River
The Chattooga River is the main tributary of the Tugaloo River. Its headwaters are located southwest of Cashiers, North Carolina, and it stretches to where it has its confluence with the Tallulah River within Lake Tugalo, held back by the Tugalo Dam...
and also in the French Broad River
French Broad River
The French Broad River flows from near the village of Rosman in Transylvania County, North Carolina, into the state of Tennessee. Its confluence with the Holston River at Knoxville is the beginning of the Tennessee River....
Valley. It is conspicuous along roadsides near the junction of North Carolina, South Carolina, and Georgia—in the vicinity of Highlands, Cashiers, and Rosman, North Carolina
Rosman, North Carolina
Rosman is a town in Transylvania County, North Carolina, United States. The population was 490 at the 2000 census. The northern terminus of U.S. Route 178 is less than one mile northwest of Rosman on U.S...
. Some outlier occurrences of silverleaf hydrangea have been locally observed in the Piedmont Region
Piedmont (United States)
The Piedmont is a plateau region located in the eastern United States between the Atlantic Coastal Plain and the main Appalachian Mountains, stretching from New Jersey in the north to central Alabama in the south. The Piedmont province is a physiographic province of the larger Appalachian division...
; these populations may have escaped from cultivation.
Taxonomy
Silverleaf hydrangea is similar to the more widespread smooth hydrangea (Hydrangea arborescensHydrangea arborescens
Hydrangea arborescens, commonly known as Smooth Hydrangea, Wild Hydrangea, or Sevenbark, is a small to medium sized, deciduous shrub up to 3 m tall that is native to the eastern United States.-Range/Habitat:...
) and ashy hydrangea (Hydrangea cinerea
Hydrangea cinerea
Hydrangea cinerea is a small to medium sized, deciduous shrub up to 3 m tall; its natural range is interior regions of the southeastern United States...
). At one time both silverleaf hydrangea and ashy hydrangea were considered subspecies of smooth hydrangea. However, most taxonomists now consider them to be separate species, and that usage is adopted here. Evidence for separating these three closely related, native hydrangeas is based largely on cross-pollination experiments conducted by Ronald Pilatowski. The crosses yielded few viable seeds at best, indicating that despite overlapping ranges and characteristics, the plants maintained their genetic
Genetics
Genetics , a discipline of biology, is the science of genes, heredity, and variation in living organisms....
purity and their unique phenotypic
Phenotype
A phenotype is an organism's observable characteristics or traits: such as its morphology, development, biochemical or physiological properties, behavior, and products of behavior...
characteristics.
Characteristics
The inflorescence of silver hydrangea is a corymb. The showy, sterile flowers (white to near white) and are comparatively abundant (2-15 per bloom) and are borne around the periphery of the corymb; they are usually greater than 1 cm in diameter.The leaves of silverleaf hydrangea are large (8 to 15 cm long), opposite, serrated, ovate
Leaf shape
In botany, leaf shape is characterised with the following terms :* Acicular : Slender and pointed, needle-like* Acuminate : Tapering to a long point...
, and deciduous
Deciduous
Deciduous means "falling off at maturity" or "tending to fall off", and is typically used in reference to trees or shrubs that lose their leaves seasonally, and to the shedding of other plant structures such as petals after flowering or fruit when ripe...
. The upper leaf surface has hairs along the veins. The lower leaf surface is densely covered with felt-like hairs, appearing bright white or silver; when viewed under magnification, these hairs are without tubercles (ashy hydrangea has numerous tubercles). These hairs are so thick that the lower surface of the leaf 's epidermis
Epidermis (botany)
The epidermis is a single-layered group of cells that covers plants' leaves, flowers, roots and stems. It forms a boundary between the plant and the external environment. The epidermis serves several functions, it protects against water loss, regulates gas exchange, secretes metabolic compounds,...
cannot be seen.
Uses
This attractive shrub has considerable landscaping potential in areas with a suitable climate and soils. Requiring cool, moist habitats in the shade, silverleaf hydrangea is not as tolerant of the heat and drought as smooth hydrangea. It is also more difficult to root from cuttings than either smooth or ashy hydrangeas. Silverleaf hydrangea produces more showy flowers than smooth hydrangea or ashy hydrangea. Silverleaf hydrangea is suitable for hardiness zoneHardiness zone
A hardiness zone is a geographically defined area in which a specific category of plant life is capable of growing, as defined by climatic conditions, including its ability to withstand the minimum temperatures of the zone...
s 4 to 9, although highly protected locations would be advisable in areas warmer than zone 6. Several popular cultivars are available (Samantha and Terri Greer).