bluejoint

Bluejoint is a common wetland reedgrass. It occurs throughout the United States and Canada, but it is absent from the south-central states, and it is uncommon in the deep south, the Great Plains, and the Great Basin. It is found in meadows, prairies, thickets, forest openings, bog edges, calcareous fens, swamps, shallow marshes, and stream banks. It grows under full or partial sun, in wet to moist areas, in loam, clay, silt, sand, or any combination of these.

Bluejoint is an erect, perennial grass that rises on one to several stems from a well-developed rhizome. Both fertile and sterile culms are produced. It often forms dense clumps. When viewed from a distance it looks wind swept, with the leaves and inflorescences blown in the same direction.

The stem (culm) is round and hollow. It is unbranched at first, but it branches from the nodes as the season progresses. It is hairless, but it may be roughened (scabrous) below the inflorescence. It can be anywhere from 12½″ to 71″ (32 to 180 cm) in height, but it is usually between 25½″ and 44″ (65 to 112 cm) in height. When growing in shallow water it often roots at the lower nodes.

The leaves are 6¼″ to 12¼″ (16 to 31 cm) long, sometimes longer, and 1 ⁄16″ to 5⁄16″ (2 to 8 mm) wide. The blades are lax (drooping) and are usually flat, but sometimes the margins are rolled inward. The upper surface is strongly rough to the touch (scabrous). It is often covered with a whitish, waxy film (glaucous), making it appear pale green or bluish green. The lower surface is scabrous. The lower part of the leaf that surrounds the stem (sheath) is open. It is usually smooth, but it is sometimes scabrous. The ligule is ⅛″ to 5⁄16″ (2 to 8 mm) long, sometimes longer. It is membranous, translucent, and irregularly cut at the top, appearing torn. On mature plants, the area where the blade meets the sheath (collar) is purplish on the sides, and the ligule is as well. This is an important identifying feature of the species. However, on young plants this feature is not always apparent.

The inflorescence is a dense, branched arrangement (panicle) of spikelets at the end of each flowering stem. It is usually 3½″ to 6¾″ (9 to 17 cm) long and ¾″ to 1 9⁄16″ (2 to 4 cm) wide, but it can be up to 10″ (25 cm) long and up to 3″ (8 cm) wide. It is pale green to purplish when young, becoming straw colored at maturity. The branches are usually 1 1⁄16″ to 2⅜″ (2.7 to 6.0 cm) long, but they can be up to 4¾″ (12 cm) long. When young, the branches are strongly ascending and the panicle is contracted. At maturity, the branches are spreading or drooping and the panicle is open.

Each spikelet is somewhat flattened and 1⁄16″ to 3⁄16″ (2.0 to 4.5 mm) long, sometimes slightly longer. The central axis of the spikelet is prolonged into a 1⁄64″ to 1⁄32″ (0.5 to 1.0 mm) long bristle (awn). The spikelet has a single floret. At the base of each spikelet there is a pair of sterile bracts (glumes). At the base of the floret there is another pair of bracts, an outer bract (lemma) and an inner bract (palea). The lemma is narrowly egg shaped and 1⁄16″to ⅛″ (1.4 to 3.8 mm) long, slightly longer than the palea. It has a 1⁄32″to ⅛″ (0.9 to 3.1 mm) long awn attached at about the midpoint. At the base of the lemma there is a tuft of long hairs. The hairs are about as long as the lemma. The floret has 3 stamens.

On var. canadensis, the most widespread and most common variety, the spikelet is ⅛″ (2.5 to 4.0 mm) long. The lemma is usually shorter than the glumes. The glumes are rounded to broadly ridged (keeled), the midvein is raised, and the tip is sharply pointed with straight sides (acute), rarely with concave sides (acuminate). The surface of the glumes may be smooth or scabrous. It is sometimes mostly smooth, scabrous only on the keel. The prickles on the keel are straight.

On var. macouniana, the spikelet is 1⁄16″ to ⅛″ (2.0 to 3.0 mm) long. The lemma is usually about as long as the glumes. The glumes are rounded, the midvein is not raised, and the tip is always acute. The surface of the glumes may be smooth or scabrous. It is sometimes mostly smooth, scabrous only on the keel. The prickles on the keel are straight.

On var. langsdorffii, the spikelet is usually ⅛″ to 3⁄16″ (4.0 to 5.0 mm) long, sometimes slightly shorter or slightly longer. The lemma is shorter than the glumes. The glumes are keeled, the tip is distinctly acuminate, and the entire surface is scabrous. The prickles on the keel are hair-like and often bent.

12½″ to 71″ (32 to 180 cm)

Wet to moist. Meadows, prairies, thickets, forest openings, bog edges, calcareous fens, swamps, shallow marshes, and stream banks. Full or partial sun. Loam, clay, silt, sand, or any combination of these.

June to August

Sources

2, 3, 4, 5, 7, 24, 28, 29, 30.

Native

Common and widespread

Most sources recognize three or four varieties based on the shape and pubescence of the glume, and on the glume length relative to the lemma length. Steyermark’s Flora of Missouri (Yatskievych, 2006) rejects the separation, stating that the differences are minor, and there is too much overlap in the features to justify recognition of the varieties. World Flora Online and Plants of the World Online do not recognize any varieties.

Calamagrostis canadensis - bluejoint
Matt Lavin

Minnesota Native Plant - Blue Joint Grass (Calamagrostis Canadensis)
MNNativePlants

Luciearl
7/4/2024

Location: Lake Shore, MN