Dichanthelium boreale (Northern Panic Grass)
|Also known as:||Northern Rosette Grass|
|Habitat:||part shade, sun; moist to dry sandy or rocky soil; prairies, meadows, shores, rock outcrops, wetland edges, forest edges|
|Fruiting season:||June - October|
|Plant height:||10 to 30 inches|
|Wetland Indicator Status:||GP: FACU MW: FAC NCNE: FAC|
|MN county distribution (click map to enlarge):|
|National distribution (click map to enlarge):|
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Erect branching cluster 2 to 4 inches long at the top of the stem, the branches spreading to ascending, with 40 to 200+ spikelets in a panicle. Spikelets are at the tips of slender, wiry branchlets, 2 to 2.2 mm (less than 1/8 inch) long, oval-elliptic, broadest at or above the middle, green to purple, and have 2 florets but appear single-flowered. In summer to fall, few-flowered secondary panicles may form in the lower and mid-stem branches that may be at least partially hidden in the sheaths.
At the base of a spikelet is a pair of bracts (glumes), the lower glume ¼ to 1/3 as long as the spikelet, pointed at the tip and 3-veined, the upper glume as long as the spikelet, 7-veined, short-hairy, blunt to pointed at the tip. Surrounding a floret is a pair of bracts (lemma and palea), the lower lemma like the upper glume and sterile; the lower palea is obscure or absent. The upper lemma is fertile, about as long as or slightly longer than the upper glume, shiny and hardened, pointed at the tip, the edges rolled around the edges of the similar palea.
Leaves and stems:
The 3 to 5 stem leaves are alternate, erect to spreading, to 4+ inches long, 5 to 13 mm (to ~½ inch) wide, flat, tapering to a pointed tip, and hairless on both surfaces but usually with a few long hairs along the edge near the base, the hairs lacking enlarged bases (not papillose). In fall, a loose rosette of basal leaves is formed, the leaves similar but much smaller than the stem leaves.
Sheaths are mostly hairless except for a fringe of long hairs along the edge; the lower sheaths are sometimes finely hairy. The ligule (membrane where the leaf joins the sheath) is a fringe of hairs about .5 mm long. Nodes are usually hairless, occasionally the lower nodes have sparse long hairs. Stems are hairless, erect to ascending, multiple from the base forming loose to dense clumps. In summer to fall, stems become more prostrate and branch from the lower and mid-stem nodes, the branches rebranching 2 or 3 times.
Dichanthelium, formerly lumped with Panicum, are cool-season grasses with two different bloom periods. The primary bloom is a terminal panicle in spring, the secondary is auxiliary panicles in summer into fall, during which time a rosette of basal leaves may also formed. The two forms can be very different from each other; spring identification is more reliably consistent but this is still a difficult genus.
Dichanthelium boreale, formerly Panicum boreale, is found in prairies, meadows, rocky shores, outcrops, and wetland and forest edges in sandy or rocky soil. It is distinguished by sheaths mostly hairless except for long hairs along the edge; usually hairless nodes; ligule a short (.5 mm) fringe of hairs; broad stem leaves (to ~½ inch wide) that are erect to spreading and hairless except for sparse long hairs along the edge near the base; open panicle with 40 to 200+ spikelets, often purple; spikelets 2 to 2.2 mm long, broadest at or just above the middle, short-hairy, blunt to pointed at the tip, the lower glume only ¼ to 1/3 as long as the spikelet. The secondary bloom is from the lower and mid-stem nodes where the panicles are few-flowered and may be only partially emerged; stems become more prostrate and basal leaves are much smaller than stem leaves. Hairs lack enlarged, pimple-like bases (not papillose).
D. boreale is fairly distinctive from the combination of spikelets about 2 mm long; leaves, nodes and sheaths lacking surface hairs; no papillose-based hairs. Most other Dichanthelium species have larger spikelets (at least 2.3 mm long), papillose-based hairs, and/or hair on leaf or sheath surfaces. Dichanthelium acuminatum subsp. lindheimeri (Hairy Panic Grass, a.k.a. D. lindheimeri) has similarly hairless leaves, nodes and sheaths, but hairs are papillose-based and spikelets are only 1.3 to 1.6 mm long.
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Photos by Peter M. Dziuk taken in Anoka and Lake counties and in his garden.
Have you seen this plant in Minnesota, or have any other comments about it?