Lolium rigidum

Scientific Name Lolium rigidum (Gaud.)
Common Names English: Annual ryegrass; German: Steifes Weidelgras; French: Ivraie raide; Spanish: Raigrás
Description L. rigidum is an annual grass forming open tussocks. The dominant habit is erect, but the species is variable in habit, ranging from dense prostrate to more open erect types.

Descriptions

Characteristic Features

The mature plant is erect, up to 100 cm (39.37 inch) in height with shiny hairless leaves, the stems are hairless and reddish-purple towards the base of the plant, particularly on younger plants.

Young Plant

The leaf blades are dark green, hairless, flat, the upper surface evenly ribbed, the lower surface smooth and shiny, 5 -25 cm (1.97 - 9.84 inch) long, 3 - 8 mm (0.118 - 0.314 inch) wide, the youngest leaves are rolled in bud.

Stems

Geniculate, reddish-purple coloration at the base of the stems extends upwards as plant matures.

Leaves

Auricles are small and narrow, the ligule translucent, 1-2 mm (0.039 - 0.078 inch), shorter than wide, truncate. Leaf sheath is hairless, with fine longitudinal ribs as in leaf blades and reddish-purple at base.

Propagatio Organs

Flowers

The inflorescence is a spike up to 30 cm (11.81 inch) in length; spikelets edge on to the rachis. Spikelets of (2 -)10 - 12 florets, laterally flattened, green, (5 -) 10 - 25 mm (0.19 - 0.39 - 0.98 inch) long. Only the terminal spikelet has 2 more or less equal glumes without awns, but terminal awns are occasionally found, probably as a result of hybridization.

Flowering Period

May - June in Europe.

Fruit

Caryopsis.

Seeds

Seeds are relatively flat, 4 - 6 mm (0.16 - 0.24 inch) long, 1 mm (0.039 inch) wide. Straw colored with seed embryo is often visible through the outer layers. Germination occurs in autumn and spring. Germination is usually in autumn, and both temperature and rainfall patterns may interact to influence emergence patterns, so that a proportion of seeds may survive and continue to emerge after crop sowing.

Viability Of Seeds

2 - 4 years.

Propagation

By seeds. It is a prolific seed producer, with as many as 645,000 seeds/m* (539,302 seeds/sq.yd) recorded in wheat. Following dissemination, innate seed dormancy lasts for about 2 months. The seeds are very light in weight and easily transported by wind.

Occurrence

Habitat

L. rigidum origniates from the Mediterranean area and is introduced to Mid and Northern Europe, southern Australia and the USA .

Soil

Warm, sandy soils.

Additional Crop Information

Mainly found in summer annual cereals, pastures and legumes fallow land, in vineyards, olive plantations, and sandy places.

Agricultural Importance

Annual ryegrass is not a very competitive weed, however seed bank numbers in many infested areas are high and it becomes established early in the growing season of grain crops, pastures and legumes. Ryegrass plants produce large numbers of tillers, prefer reduced tillage systems, evlove resistance to many grassweed herbicides and non selective herbicide.

Control

Integrated Crop Management

Intensive grazing in infested pastures, deep soil tillage (burying of weed seed below 5 cm; 1.97 inch) can greatly reduce the amount of ryegrass germinating with or in the crop.

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