Sorghum halepense

Scientific Name Sorghum halepense (L.) Pers.
Synonyms Andropogon halepensis (L.) Brot., Andropogon miliaceus Roxb., Holcus halepensis L., Milium halepense (L.) Cav., Sorghum giganteum Edgew, Sorghum miliaceum (Roxb.) Snowden
Common Names English: Johnson grass; French: Herbe de Cuba, sorgho d'Alep, German: Aleppohirse, Wilde Mohrenhirse; Spanish: Canota, sorgo, zacate johnson
Description S. halepense is a perennial grass with extensively creeping, fleshy rhizomes which are covered with brown scale-like sheaths, up to 1 cm (0.39 inch) in diameter, 2 m (6.56 ft) in length, and often root from the nodes. The fibrous root system branches freely to depths of 1.2 m (3.93 ft).

Descriptions

Characteristic Features

Ribbed leaf sheath, conspicuous midrib, large, purplish panicle and extensive rhizome system.

Young Plant

Unbranched flowering stems, 0.5-3.0 (-4.0) m (1.64 - 9.84 - 13.12 ft) tall, 0.5-2.0 cm (0.19 - 0.78 inch) in diameter, often with basal adventitious prop roots, nodes sometimes with fine hairs.
Youngest leaf is rolled.

Stems

Flowering stems are unbranched, 0.5-3.0(-4.0) m (1.64 - 9.84 - 13.12 ft) tall, 0.5-2.0 cm (0.19 - 0.78 inch) in diameter, often with basal adventitious prop roots, nodes sometimes with fine hairs.

Leaves

Leaf blades, 20-60 cm (7.87 - 23.62 inch) long, 1.0-3.3 cm (0.39 - 1.56 inch) wide, prominent midribs and white, whitish midvein, many nerved and hairless.
Membranous ligule with hairy fringe, 2-5 mm (0.078 - 0.19 inch) long.
No distinct auricles.
Ribbed, hairless leaf sheaths with overlapping margins.

Propagation Organs

Flowers

Inflorescence pale green to purplish, hairy, pyramidal, many branched panicle, 15-50 cm (5.9 - 19.68 inch) long.
Primary branches up to 25 cm (9.84 inch) long, usually without spikelets for 2-5 cm (0.78 - 1.96 inch) from the base.
Spikelets usually in pairs but towards the top of the inflorescence in threes, one spikelet of each pair or triplet is sessile and perfect with stamens and stigma, others stalked and sterile or only carry stamens. Fertile spikelets are ovoid, hairy, 4.5-5.5 mm (0.17 - 0.21 inch) long.
Awns if present are 1-2 cm (0.39 - 0.78 inch) long, twisted and abruptly bent.
Glumes reddish brown to shiny black, glossy and finely lined.

Flowering Period

S. halepense begins to flower approximately two months after growth commences. The exact flowering time depends on temperature, plant vigor and photoperiod.

Fruit

The grain remains enclosed by glumes 4-6.6 mm (0.16 - 0.25 inch) long, 2-2.6 mm (0.078 - 0.10 inch) wide. The glumes are reddish brown to shiny black, glossy and finely lined on the surface.

Viability of Seeds

6 years. Seeds remain viable after passing through the digestive system of animals.

Propagation

Mature seeds are readily shed and can be carried over short distances by wind or rain water run-off, and can travel over longer distances in canals from where this species may be introduced to new sites with irrigation water. Most seeds do not germinate during the year when they are produced, but germinate readily in the following year. Seedlings arise from seeds in the top 7 cm (2.75 inch) of the soil, but seeds buried as deep as 15 cm (5.9 inch) still can emerge. Vegetative reproduction from potentially vast rhizome systems results in difficult to control infestations of primarily row crops.

Occurrence

Habitat

In the eastern Mediterranean, where it is probably native, S. halepense is found in dry open habitats. It is now found in most of the tropical and warm temperate regions of the world but is best adapted to humid summer rainfall areas in the subtropics rather than to areas which are strictly tropical. The lack of cold tolerance has prohibited the spread of S. halepense into areas with cooler climates. The species can be found on arable land, wasteland and roadsides, and along stream or irrigation canal banks.

Soil

Wide variety of soil types, however fertile porous soils support larger plants than poorly drained clay soils. Soils with a pH of between 5 and 7.5 are ideal for Johnson grass.

Additional Crop Information

Also orchards and pastures.

Agricultural Importance

The ability of S. halepense to persist and compete with crops as a serious weed problem is related to the vigorous rhizome system. S. halepense is most commonly a major problem in subtropical crops which are planted in wide rows (cotton, corn, sorghum, soyabean and sugarcane). It can be a problem in closely spaced crops including sugar beet and wheat in warm temperate areas, and also in permanent crops, orchards and pastures.

Control

Useful non-chemical contribution to Integrated Weed Management

Restrictions in land disturbances in the surrounding area and in the pre-controlled site will reduce the likelihood of invasion by the surviving rhizome fragments. As a last step of conventional seedbed preparation rhizomes need to be pulled out of the field with proper mechanical equipment unless weather conditions ensure that rhizomes will get controlled by sufficient desiccation requiring a loss at least 80% of its fresh weight.

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