Ischaemum rugosum

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Ischaemum rugosum, commonly called saramollagrass, is a fast-growing annual grass found in the tropical and subtropical parts of Asia. It grows in moist areas such as marshes, wet grasslands, riverbanks, and drainage ditches. The plant forms loose clumps and can reach 10–100 cm tall. It is native to Asia but has become an invasive weed in Madagascar and in many parts of South America, and it can seriously affect rice paddies.

Identification basics: Ischaemum rugosum has a distinctive wrinkled lower glume on the sessile spikelet, with 4–7 horizontal ribs. The plant produces brown, ovoid grains about 2 mm long. The culms are wrapped by papery leaf sheaths, and the leaves are narrow, up to about 30 cm long. The inflorescence consists of two back-to-back racemes, each 3–12 cm long, with spikelets in pairs—one fertile and sessile, the other sterile and pedicelled.

Growth and ecology: The species tolerates wet soils and thrives in moist habitats. In laboratory conditions, germination is very high (around 97.5%) when the temperature is 20–30 °C, but it requires moist soil and will not germinate in darkness.

Impact and control: It is a significant weed in rice fields, capable of reducing yields—reports from India show losses of up to about 69%. Young shoots can resemble rice, complicating early control. Some populations have developed resistance to common herbicides, so effective management often relies on cultural methods such as mulching with rice residue and shallow tillage, used as part of an integrated weed-management approach.

Notes: The name Ischaemum rugosum reflects its wrinkled glume (rugosum). The species has various regional names and a long history of use as forage in some areas, though its agricultural impact today is mainly as a troublesome weed in moist rice-growing regions.