Dichanthelium xanthophysum (Slender Panic Grass)
|Also known as:||Slender Rosette Grass, Yellow Panic Grass, Pale Panic-grass, Pale-leaved Rosette-panicgrass, Slender Panicum|
|Habitat:||part shade, sun; moist to dry sandy or rocky soil; forest edges, Jack pine stands, prairies, rock outcrops, cliffs, rocky shores|
|Fruiting season:||June - July|
|Plant height:||8 to 24 inches|
|Wetland Indicator Status:||none|
|MN county distribution (click map to enlarge):|
|National distribution (click map to enlarge):|
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Slender, erect, branching cluster 2 to 6 inches long at the top of the stem, the branches all appressed, with few to several spikelets (flower clusters) per branch, usually fewer than 40 spikelets in a panicle. Spikelets are short-stalked, 3.2 to 4.1 mm (to ~1/6 inch) long, broadest near the tip, and have 2 florets but appear single-flowered. In summer to fall, few-flowered secondary panicles may form in the lower and mid-stem nodes that are at least partially hidden in the sheaths.
At the base of a spikelet is a pair of bracts (glumes), the lower glume about half as long as the spikelet, pointed at the tip, the upper glume as long as the spikelet, 7-veined, hairless or sparsely short-hairy, blunt to rounded at the tip. Surrounding a floret is a pair of bracts (lemma and palea), the lower lemma like the upper glume and sterile or staminate; the lower palea is often absent. The upper lemma is fertile, shorter than the upper glume, shiny and hardened, blunt at the tip, the edges rolled around the edges of the similar palea.
Leaves and stems:
The 3 or 4 stem leaves are alternate, mostly erect, to 6+ inches long, 7 to 23 mm (to .9 inch) wide, flat, with a long taper to a pointed tip, and hairless on both surfaces but with a few long hairs along the edge near the base, the hairs with enlarged, pimple-like bases (papillose). In fall, a loose rosette of basal leaves is formed, the leaves similar but somewhat smaller than the stem leaves.
Sheaths are hairless or short-hairy, usually with papillose-based hairs along the edges. The ligule (membrane where the leaf joins the sheath) is a fringe of hairs .3 to .5 mm long. Nodes are hairless to sparsely hairy. Stems are hairless to minutely hairy, single or a few from the base forming loose clumps, erect or prostrate from the base and rising at a lower node (geniculate). Branches may arise from the lower and mid-stem nodes in late summer to fall.
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 xanthophysum, formerly Panicum xanthophysum, is most often found in or near forested areas in sandy or rocky soil. It is distinguished by its loosely clump-forming habit; sheaths hairless to densely hairy, commonly fringed along the edges, the hairs with enlarged, pimple-like bases (papillose); ligule a very short (.3 to .5 mm) fringe of hairs; broad stem leaves (to nearly 1 inch wide) that are erect to ascending and hairless except for sparse papillose-based hairs along the edges near the base; slender panicle with erect branches and fewer than 50 spikelets; spikelets 3.2 to 4.1 mm long, broadest near the tip, hairless to sparsely short-hairy, the lower glume about half as long as the spikelet. The secondary bloom is from the lower and mid-stem nodes where the panicles may be only partially emerged; basal leaves are like stem leaves but somewhat smaller.
Most similar is Dichanthelium leibergii (Leiberg's Panic Grass), which can have a very similar form with somewhat broad (to ~½ inch) erect leaves, a very short ligule, hairy spikelets and lower glumes half (or more) as long as the spikelet, but the hairs on the spikelets are longer and have papillose bases, and leaves tend to be at least sparsely hairy on both surfaces, though this is variable, and sometime the panicle branches are erect but more often they are spreading. Somewhat similar is Dichanthelium boreale (Northern Panic Grass), which has broad (to ~½ inch) and hairless leaves and a very short ligule, but has spreading panicle branches, spikelets only about 2 mm long, and hairs are not papillose-based. Both of these species are more often found in open prairies or meadows, less often in open woods.
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- Slender Panic Grass plant
- Slender Panic Grass plants
- Slender Panic Grass plants
- close-up of ligule
- comparison of Dichanthelium xanthophysum and D. leibergii spikelets
Photos by Peter M. Dziuk taken in Lake and Roseau counties.
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