Plants annual; cespitose. Culms 30-300+ cm, glabrous or sparsely pubescent below the nodes, branching above the bases. Leaves mostly cauline, not aromatic; sheaths sometimes with papillose-based hairs; auricles absent; ligules membranous, ciliate; blades flat. Inflorescences terminal and axillary, solitary rames with more than 1 spikelet unit, spikelets partially embedded in the rame axes; disarticulation in the rame axes. Spikelets heterogamous, in sessile-pedicellate pairs, dorsally compressed, unawned. Sessile spikelets with 2 florets; lower glumes coriaceous, smooth or scabridulous, not pitted, 2-keeled, narrowly winged above; upper glumes coriaceous, 1-keeled, winged; lower florets staminate or sterile; upper florets bisexual; lemmas and paleas hyaline; anthers 3; ovaries glabrous. Pedicels thick, fused to the rame axes. Pedicellate spikelets sterile or staminate; glumes herbaceous. Caryopses with a hard endosperm. x = 9, 10. Named for Christen Friis Rottboell (1727-1797), a Danish botanist.