Setaria viridis

Scientific Name Setaria viridis (L.)Beauv.
Common Names English: Giant green foxtail, green bristlegrass, green bristle grass; German: Grüne Borstenhirse; French: Sétaire verte; Spanish: Almorejo
Description Annual, tufted warm season grass, closely related to cultivated Setaria species for grain and forage use, originates from Eurasia.

Descriptions

Characteristic Features

Mature spikelets fall entire, leaf sheath and leaf blade virtually glabrous, green at the youth stage, during maturation red.

Young Plant

Youngest leaf is rolled. Leaves about 20 cm (2 - 40 cm) (0.78 - 15.74 inch) long by 10 mm (4 - 25 mm) (0.147 - 0.98 inch) long. Leaf-blade surface scaberulous; glabrous.

Stems

More-or-less erect, thin and hairless up to 70 cm, rarely 100 cm (27.55 inch, rarely 39.37 inch) high.

Leaves

Leaves wide, flat, acuminate, light green, sometimes reddish-purple, drooping, distinctly but finely veined with prominent mid-vein below (keeled), mid-vein white or light green, scabrous above, usually glabrous below.
Ligule a fringe of hairs up to 2 mm (0.078 inch) long, fused at the base.
No auricles.
Sheaths slightly compressed, sometimes purplish at the base, the margins noticeably ciliate.

Propagation Organs

Flowers

Dense spike-like panicle inflorescence, erect or slightly nodding at the tip, rachis often pilose.
Spikelets in very short panicle branches, each spikelet elliptical, subtended by 1 to 3 bristles 5-10 mm (0.19 - 0.39 inch) long, usually green, rarely purple, antrorsely barbed.
Lower glume smaller than spikelet, upper glume 5-6-nerved.
Lower lemma sterile, like the upper glume, upper lemma fertile, finely rugose.

Flowering Period

Summer-early autumn, flowering after 26 days growth in an 8-hour photoperiod, after 62 days in a 16-hour photoperiod.

Fruit

Very finely transversely wrinkled or ridged.

Seeds

Germination in late spring, emerges later than Echinochloa crus-galli. Freshly shed seed is germinating immediately. Optimum temperature for germination is 20 - 25 °C (68 - 77 °F) and most germination occurs from the top 1 - 2 cm (0.39 - 0.78 inch) soil layer.

Viability of Seeds

Seed viability up to 40 years.

Propagation

Seeds are spread with contaminated crop seeds and by animals. The weed is able to tiller and to produce seeds within 2-3 months.

Occurrence

Habitat

Temperate and subtropical zones.

Soil

S. viridis prefers light and coarse-textured soils, all soils including black clays. It prefers high nitrogen levels.

Additional Crop Information

Also in gardens, cereals, vegetable crops, ornamentals, grassland and forestry, waste places, disturbed areas and along roads.

Agricultural Importance

Individual plants cause only moderate yield reduction, however, S. viridis often occurrs in high densities. It can escape control by late emergence after herbicides had been applied.

Control

Useful non-chemical contribution to Integrated Weed Management

Rotations with winter annual crops or cover crops, mechanical weed control methods will result in limited control success.

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