American common reed

LC - Least Concern

N4 - Apparently Secure

SNR - Unranked

not listed

FACW - Facultative wetland

FACW - Facultative wetland

FACW - Facultative wetland

American common reed is a perennial, reed-like grass that rises on a single stem from an underground stem (rhizome) and fibrous roots. It slowly forms large colonies that are not dense enough to crowd out all other species. The rhizome is stout, almost perfectly round in cross section, and usually under ⅝″ in diameter.

The stem (culm) is annual, stout, hollow between the nodes, and unbranched. It is 3 ⁄16″ to ⅝″ in diameter and usually 4′ to 6½′ in height, but may be 8½′ tall or taller. It is flexible, leafy, and hairless, shiny, smooth, and light green to maroon, sometimes maroon only at the nodes. It is sometimes covered with a whitish, waxy film (glaucous). There are often small black spots between the nodes caused by a native fungus. In the spring and summer the lower part of the culm, when the leaf is removed, is reddish to chestnut brown. In the winter it is light chestnut brown to light brownish-gray.

The leaves are alternate, ascending to arching, yellowish-green, and deciduous, falling away in the winter and exposing the culm. The blades are linear lance-shaped, flat, flexible, 6″ to 24″ long, and ¾″ to 1½″ wide. They taper to a slender, thread-like point at the tip. The upper and lower surfaces are hairless. The upper surface has numerous parallel veins. The midvein is noticeably thickened on the underside. The lower part of the leaf that surrounds the stem (sheath) is usually hairless, sometimes hairy along the margins. The margins of the sheath overlap. Where the leaf blade meets the sheath there is a thin, pliable appendage (ligule). The ligule is 1.0 to 1.7 mm long and has a fringe of white hairs. In the winter any sheaths remaining on the culm pull away easily.

The inflorescence is a large, dense, plume-like cluster (panicle) of numerous ascending to drooping branches. The panicle is egg-shaped to lance-shaped in outline, 6″ to 14″ long, and 3″ to 8″ wide. It is silky and purplish or reddish when in bloom, light tan to dark brown when in fruit.

Each spikelet is egg-shaped to inversely triangular on outline, somewhat flattened, and ⅜″ to ⅝″ long. One spikelet consists of an upper and lower protective bract (glume) and 3 to 8 florets. The lower 1 or 2 florets are male (staminate), the upper 1 or 2 are reduced in size and nonfunctional (sterile), and the remaining ones contain both male and female parts (bisexual). The florets are closely spaced along a zigzagged central axis (rachilla). The rachilla is densely covered with silky, ¼″ to ⅜″ long hairs. The glumes have 1 to 3 veins, are hairless, and are shorter than the florets. The lower glume is ⅛″ to ¼″ long. The upper glume is much longer, 3 ⁄16″ to 7 ⁄16″ long.

Each fertile floret consists of an outer protective bract (lemma), an inner protective bract (palea), and reproductive parts. The lemma is 5 ⁄16″ to ½″ (8 to 13.5 mm) long, is rounded on the back, and has 3 veins. The palea has 2 veins. Bisexual florets have 3 stamens with purplish anthers. Staminate florets may have fewer stamens.

Fruits are seldom produced and when they are they rarely mature. A mature fruit (caryopsis) is 1 ⁄16″ to ⅛″ long, oblong, and circular or slightly flattened in cross section, with a short beak at the tip.

4′ to 16′

Wet and muddy areas. Marshes, sloughs, lake shores, and alongside streams.

July to August

Sources

3, 4, 7, 28, 29, 30.

Native

Very common and widespread in Minnesota

Plant

Culm

Infructescence