Sorghum halepense

Name and classification

Sorghum halepense L.
Family Poaceae, Tribe Andropogoneae

NOTE: This species is actionable only when found in field or vegetable seed for planting; tolerance applies.

Common names

Johnsongrass

Disseminule

sessile spikelet with attached pedicel and rachis segment, sessile spikelet with attached pedicellate spikelet and rachis segment, sessile spikelet with two attached pedicellate spikelets, sessile spikelet with two attached pedicels, sessile spikelet with one or more of these parts, apex, or base of spikelet broken or broken off, or caryopsis; disarticulation at base of sessile spikelet, tip of rachis segment, and tip of pedicel

Description

Spikelets heteromorphic. Sessile spikelet dorsally compressed, 3.8–6.5 mm long, 1.5–2.3 mm wide, glumes indurate, shiny, straw-yellow to dark reddish brown, consisting of one fertile floret and one basal sterile lemma. Spikelet callus pubescent; pedicels with silky hairs. Lower glume coriaceous, length of spikelet, its margins enclosing upper glume, 2-keeled near apex, apex dentate, 3-fid; upper glume coriaceous. Sterile lemma hyaline. Fertile lemma hyaline, 2–4 mm long; +/– awned, awn to 13 mm long, geniculate, twisted. Palea present or absent or minute. Pedicellate spikelet(s) dorsally compressed, glumes membranous to coriaceous, 4–6.5 mm long, containing empty or staminate lemmas. Caryopsis reddish brown, 2.5–3 mm long, dorsally compressed.

Identification considerations

Spikelets are frequently found with apices broken off.

Similar species

Sorghum almum Parodi (non-FNW)

Sorghum bicolor (L.) Moench nothosubsp. drummondii (Steud.) de Wet ex Davidse (i.e., sudangrass) (non-FNW)

Identification characters: (Spikelet length differences easier to discern in bulk samples, and spikelet shape and caryopsis relative length may be difficult to determine if apices are broken off.)

Distribution

widespread; found in most agricultural regions of the world

native from southern Eurasia and northern Africa east to India

Habitat

tropical and temperate climates, best adapted to warm humid subtropics; a weed of arable land, along irrigated canals, roadsides, waste places

General information

Sorghum halepense is an erect, perennial, rhizomatous grass, to 3.5 m tall. It is a principal weed of corn, cotton, and sugarcane, and a weed of many crops throughout the world including the United States. The disseminule is the principal means of spread, by water, wind, sticking to fur of animals and ingestion by animals, and commercial seed contamination. Control of S. halepense is difficult because new plants sprout from nodes on its extensive root-rhizome network. Sorghum halepense is one of ten species covered under the Federal Seed Act for which tolerance is applicable to its introduction (7 CFR 361.6(a)(2)).

portion of inflorescence (left); terminal spikelet with two pedicellate spikelets (middle); spikelet with pedicellate spikelet and rachis segment (right)

portion of inflorescence (left); terminal spikelet with two pedicellate spikelets (middle); spikelet with pedicellate spikelet and rachis segment (right)

ventral view of spikelets with pedicel and rachis segment

ventral view of spikelets with pedicel and rachis segment

dorsal view of spikelets

dorsal view of spikelets

spikelets with apices broken off

spikelets with apices broken off

caryopses in dorsal view (left) and ventral view (right)

caryopses in dorsal view (left) and ventral view (right)

caryopses in side view

caryopses in side view