Leslie Cagle
Ecology Major
University of Georgia
Athens
lcagle@arches.uga.edu OR
cagle.leslie@epa.gov
Photographed by W. H. Duncan on March 7, 1975 in Accomack County, Va.
Courtesy of The University of Georgia Herbarium. Copyright Department
of Botany, UGA, Athens.
COMMON NAME:
Milkweed; Swamp Milkweed
HIGHER TAXA:
IDENTIFICATION:
The A. incarnata
is a perennial that is four
to five feet in height with pink to pinkish purple hourglass shaped flowers.
The flowers are about 1/3 inch long and grow in clusters upon the smooth,
branched stems. Each flower has five greenish sepals turned downward,
five petals, five stamens associated with the central column, and pistols
with two ovaries. The A. incarnata has leaves that are
mid green and grow up to four inches long and up to one inch wide.
They are narrow with a rounded base and a pointed tip (lance shaped).
The swamp milkweed is the only wetland milkweed with milky sap, opposite,
lanceolate leaves, and flowers of this color, as opposed to shades of orange.
The flowers are followed by an erect fruit up to three inches long.
These fruits are pods containing numerous seeds with silky hairs.
Click here
to link to a site with another picture of a blooming swamp milkweed.
Click here
to
link to a site with a picture of a fruiting one. Linnaeus is the
authority who described this species in 1753. The scientific reference
where this is discribed is the Index Hortensis and a scientific
reference that includes the species with an identification key is the Popular
Encyclopedia of Plants. A paratype is located at the UGA herbarium
in Athens, Ga.
GEOGRAPHY:
|
STATUS | REFERENCES |
North America:
Continental United States; Canada |
Yes | Northern Prairie Wildlife Research Center |
Eastern North America:
United States east of the Mississippi; Ontario and eastern Canada |
Yes | Northern Prairie Wildlife Research Center |
Southeastern United States:
AL AR DE DC FL GA KY SC TN VA WV |
Yes, with the
exception of FL |
Northern Prairie Wildlife Research Center |
Southern Appalachian States:
AL GA KY MD NC SC TN VA WV |
Yes | Northern Prairie Wildlife Research Center |
Coastal Plain | Widespread
excluding southeast GA |
Northern Prairie Wildlife Research Center |
Piedmont | Widespread | Northern Prairie Wildlife Research Center |
Blue Ridge Mountains | Widespread | Northern Prairie Wildlife Research Center |
Great Smoky Mountains National Park | Yes | Northern Prairie Wildlife Research Center |
Ridge and Valley | Yes | Northern Prairie Wildlife Research Center |
Cumberland Plateau | Yes | Northern Prairie Wildlife Research Center |
Georgia | Widespread | Northern Prairie Wildlife Research Center |
Clarke County, Georgia | Yes | UGA Herbarium Specimens |
According to many sources, swamp milkweed grows in USDA zones 4a to 9a. Click here to link to a site with a map explaining the USDA Plant Hardiness Zones. Click here to link to a site illustrating where A. incarnata grows in the continental United States.
NATURAL HISTORY:
As its common name implies, the swamp milkweed grows
around wet environments. The water requirement is from low to high.
It will tolerate poorly drained soil, but will grow better in a moist
but well drained area. Full sun exposure and fertile soil are also
needed to grow. The sweet smelling flowers bloom from June to August
and attract a lot of insects. The shape of the flower requires that
the insect walk through pollen masses before it can reach the nectar.
When the insect leaves, it carries with it pollen from that flower. When
it lands on another flower of the same species, it brings about cross-pollination
which is one way that A. incarnata reproduces. By fall, the
flowers are no longer there and are replaced with large, rough seed pods.
When the pods ripen and burst open, the wind scatters the seeds.
The seeds have tufts of hair to catch the wind that carries them to a new
location. Milkweeds can also reproduce vegetatively
from its underground roots. This is a type of self reproduction which
the plant produces clones of itself.
HOW TO ENCOUNTER:
Since
the plant is known to grow in wet areas, you can find it on banks and flood
plains of lakes, ponds and waterways, marshes, and swamps. You can
also find it growing on roadsides and in fields where the conditions are
tolerable. The best time to try to locate the plant would be from
June to August, when it is in bloom. If you are unfamiliar with identifying
one, you would have a better chance of identifying it by its cluster of
pink flowers. The swamp milkweed is the only one of the milkweeds
with flowers of this color. When not in bloom, it can be mistaken
for one of its close relatives of the milkweed family, since they could
possibly grow in the same type of area. Click here
to learn more about the genus, Asclepias, and click here
to learn more about the milkweed family, Asclepiadaceae. Swamp Milkweed
is also easy
to grow and many gardeners like to use it in their meadow gardens,
wildflower gardens, and as a perennial boarder. Click here
to link to a site that sells A. incarnata seeds if you are interested
in making it an addition to your garden. If you grow swamp
milkweed, butterflies will come! Click on the butterfly to find out
other flowers that they like.
Baskin, Jerry M. "Milkweed." The World Book Encyclopedia. 1998
Brickell, Christopher. The American Horticulture Society Encyclopedia of Gardening Plants. Portland, Oregon: Timber Press, 1994.
Everett, T.H. Encyclopedia of Gardening. New York: Greystone Press, 1960.
Griffiths, Mark. Index of Garden Plants. Portland, Oregon: Timber Press, 1994.
Heywood, Vernon H. "Asclepias." Popular Encyclopedia of Plants. Cambridge: Cambridge University Press, 1982.
Huxley, Anthony. The New Royal Horticulture Society Dictionary of Gardening. New York: The Stockton Press, 1992.
"Milkweed." Encyclopedia Americana: International Edition. 1998.
Northern Prairie Wildlife Research Center. "Swamp Milkweed (Asclepias Incarnata)." Midwestern Wetland Flora. Online.
Parker, Helen. Eyewitness Garden Handbooks: Perennials. New York: DK Publishing, Inc., 1996.
Smith, Gertrude. "Milkweed." Collier's Encyclopedia. 1997.
Trehane, Piers. Index Hortensis: Perennials. Wimborne: Quarterjack Publishing, 1989.
Wright, Michael. The Complete Handbook of Garden Plants. New
York: Facts On File, 1984.