Leersia oryzoides (L.) Sw.

Rice Cutgrass


CC = 3
CW = -5
MOC = 76

© SRTurner

Family - Poaceae/Oryzeae

Habit - Rhizomatous perennial grass.

Stem - Flowering stems 50-170 cm long, mostly spreading, circular in cross-section or nearly so, the joints hairy.

Leersia_oryzoides_stem.jpg Stem with spinelike hairs.

© SRTurner

Leersia_oryzoides_stem2.jpg Stem and node.

© SRTurner

Leaves - Sheaths roughened with minute stiff, spinelike, downwardly pointed hairs. Leaf blades 10-30 cm long, 6-15 mm wide, the surfaces strongly roughened with minute, stiff, spinelike hairs, the margins noticeably sawtoothed with stiff, spinelike hairs.

Leersia_oryzoides_leaf1.jpg Leaf.

© SRTurner

Leersia_oryzoides_leaf2.jpg Leaf base, abaxial.

© SRTurner

Leersia_oryzoides_leaf2a.jpg Leaf with sawtooth margin.

© SRTurner

Inflorescence - Open panicles with spreading, spikelike branches. Lowermost branches 2-4 per node, with strongly overlapping spikelets oriented toward one side of the branch.

Leersia_oryzoides_inflorescence.jpg Inflorescence.

© SRTurner

Leersia_oryzoides_inflorescence2.jpg Inflorescence axis and branches.

© SRTurner

Leersia_oryzoides_inflorescence3.jpg Inflorescence branches.

© SRTurner

Spikelets - Spikelets 4-7 mm long, 1.5-2.0 mm wide, strongly flattened, oblong to narrowly elliptic, 2.5-4.0 times as long as wide, the lemma and palea with an "eyelash-like" fringe of hairs along the keel and other nerves, otherwise glabrous. Glumes absent. Stamens 3.

Leersia_oryzoides_spikelets2.jpg Spikelets. Both anthers and styles are protruding. The styles are the pipecleaner-like structures.

© SRTurner

Leersia_oryzoides_spikelets1.jpg Spikelets.

© SRTurner

Fruits - Caryopses 3.0-3.5 mm long, uneven in outline.

Flowering - June - October.

Habitat - Swamps, bottomland forests, sloughs, marshes, fens, streambanks, pond margins, ditches, often emergent aquatics.

Origin - Native to the U.S.

Lookalikes - L. lenticularis.

Other info. - The common name of this grass, "rice cutgrass," is well-deserved. The stems and leaves are covered with retrorse hairs which are tiny, but numerous, stiff, and sharp. These give the foliage a sawtooth aspect which is too small to be seen at a casual glance, but which can be devastating to bare skin. Careless walking through a field having much of this species present will result in a maze of scratches and welts, often deep enough to draw blood, across areas of exposed skin. Knowledgeable hikers and naturalists will venture into wet, grassy fields only with caution, or with all skin covered. The "rice" part of the common name derives from a faint resemblance of the species to rice (Oryza sativa).

This rather unpleasant species is common in wet areas across Missouri and the continental U.S., and uncommon in the more arid regions of the country. Aside from the extreme scabrousness of the stems and leaves, it is recognized by the distinctive spikelets, which are arranged in stacks along one side of each inflorescence branch. They are fringed with curved hairs, which are often likened to eyelashes. Compared to the sibling species L. lenticularis, L. oryzoides has narrower spikelets (2-3 times as long as wide).

Photographs taken at B. K. Leach Memorial Conservation Area, Lincoln County, MO, 9-13-2021 (SRTurner).