Taxonomic Description of Sorghum halepense (L.) Pers. JOHNSONGRASS:
"Culms 50-150 cm. tall, from extensively creeping scaly rhizomes; blades mostly less than 2 cm. wide; panicle open, 15 to 50 cm. long; sessile spikelet 4.5 go 5.5 mm long, ovate, appressed-silky, the readily deciduous awn 1 to 1.5 cm. long, geniculate, twisted below; pedicellate spikelet 5 to 7 mm. long, lanceolate" (Hitchcock, 773, 1971).
Authorities' full names: (Carl Linnaeus 1707-1778) Christian Hendrik Persoon 1761-1836
Some of the more uncommon common names of Sorghum halepense
include, in addition to Johnsongrass, Aleppo, Means-grass,
and Egyptian Millet (Bailey & Bailey, 1976).
The original species of Sorghum halepense was described
by Persoon in Synopsis plantarum in 1817 (Jackson, 1893).
This book was locally unavailable and was not visited, thus the
location of original collection and deposition are unknown. The
complete reference for the book is included in the reference list
(see Persoon, 1817).
Geography:
Worldwide, there are about 30 species of Sorghum, distributed
primarily in the tropical and subtropical climate zones, but also
found in temperate climate zones, where they are both cultivated
and wild. Since they grow as both shade species and in open habitats,
they are very abudant in the above climate zones. Sorghum halepense
(L.) Pers. is more limited to open habitats and is only found
marginally in shaded areas (Watson & Dallwitz, 1992).
Its primary distribution in this country is due to cultivation
and is found primarily in the Southeast (Uphof, 1968).
The following is a table detailing its presence or absence, ranging
from North America to habitats within Sam's Farm, a University
of Georgia 40 hectare plot in Clarke County, Georgia:
| ||
| North America:
Continental United States; Canada | ||
| Eastern North America:
United States east of Mississippi; Ontario and eastern Canada | ||
| Southeastern United States:
AL AR DE DC FL GA KY MD NC SC TN VA WV | ||
| Southern Appalachian States:
AL GA KY MD NC SC TN VA WV | ||
| Coastal Plain | Jones & Coile, 1988 | |
| Piedmont | Jones & Coile, 1988 | |
| Blue Ridge Mountains | ||
| ||
| Ridge and Valley | ||
| Cumberland Plateau | ||
| Central Arch | ||
| Georgia | ||
| Clarke County, Georgia | ||
| Sams Farm | ||
| ||
| ||
| ||
| ||
Natural History:
Sorghum halepense (L.) Pers. grows as a rhizomatous perennial, reproducing both sexually and apomictically, the latter being a form of asexual reproduction involving the production of a self-contained spore-like "seed". Sexual reproduction involves both inbreeding and outbreeding, with periods of flowering persisting from early June through October (de Wet, 1978).
Two different stands of Sorghum halepense
(L.) Pers., nonflowering(l) and flowering(r). Photos by: J.David
Daniel at Sam's Farm (970802)
Sorghum halepense (L.) Pers. is native to the Mediterranean
region of the world, where it grows as a perennial grass (Uphof, 1968).
It was purposely introduced into the warmer parts of North America
as a foraging crop. It is especially well established in the Southeastern
parts of the United States and is cultivated in the cooler parts
of the United States (Gould, 1983).
Where it grows wild, it can be found in savannas, along forest
margins, in alluvial plains, and especially in disturbed ground
(Watson & Dallwitz, 1992). In
the Southeast, it has become a problem in some areas, eliminating
much of the grass diversity by completely taking over pastures
and persisting despite efforts at eradication (Uphof, 1968).
Additionally, Sorghum halepense (L.) Pers. is a very quick
grower in full sun and as it reaches complete adult forms, can
develop cyanogenetic compounds in amounts significant enough to
cause prussic acid poisoning in grazing animals (Gould, 1983;Bailey & Bailey, 1976).