Lax-Flowered Witchgrass

In August of 2013, I documented Lax-Flowered Witchgrass, also known as Open-Flower Rosette Grass (Dichanthelium laxiflorum), which is classified as highly state rare, not yet ranked (S1?) by the Maryland Department of Natural Resources, Natural Heritage Program.  The plants were observed along the top-of-bank of a first-order stream on a riparian woodland flat, adjacent to the bench of a rocky slope.

Lax-Flowered Witchgrass, also known as Open-Flowered Rosette Grass (Dichanthelium laxiflorum Synonym – Panicum laxiflorum) is a native herbaceous perennial that occurs from Maryland, south to Florida and west to Texas.  Maryland represents the northern extent of this southeastern species.  The Maryland DNR Natural Heritage Program has classified this plant as being Highly State Rare, Not Yet Ranked (S1?).  The plant can be found in dry, upland forests of the piedmont, rocky woodlands, open woods and forest edges and occur as scattered or individual plants.

The grass clump typically forms as a round rosette, which persists by rhizome and spreads by seed.  Seeds may be eaten by ground nesting songbirds and game birds such as wild turkey.  The plant is poor forage for deer and is not generally considered palatable or preferred as deer browse.

The plant has two distinct blooming periods (typical of Panicums), flowering (inflorescence) in April – July and again in June – September.  The leaf nodes have evident soft spreading hairs.  The stems and leaves have hairs as well, with the stem hairs usually pointing downward.

The plant has been documented on several occasions along the C & O Canal in Montgomery County, with Smithsonian herbarium samples dating from 1879, 1904, 1932, 1960 and 2008.  The National Park Service, who manage Great Falls, Carderock and the C &O Canal have documentation of this RTE plant species within their natural resources management plan as well as the recently released/approved Natural Resources Management Plan for Natural Areas in M-NCPPC Parkland in Montgomery County, February 2013.

In performing a literature search regarding the plant, it appears that hazards related to protection are unknown, but that possibly herbivory/grazing may represent a threat, especially if deer should exceed their biological carrying capacity.

Many riparian stream valley corridors, floodplains and bottomlands in Montgomery County are negatively affected by the non-native invasive known as stilt grass (Microstegium vimineum).  This grass was not observed immediately up or downstream of the rare plant location.  As a disturbance species, stilt grass can readily occupy, spread and overwhelm, which may represent a future threat through competitive exclusion, if/as it may become established.

 

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Broad view photo, without camera flash, of Dichanthlium laxiflorum.

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Broad view photo, with camera flash, of Lax-Flowered Witchgrass.

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Overview, without flash.

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Overview, with flash.

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Close-up showing leaf structure, leaves, sheaths, nodes, pubescence and inflorescence.

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Close-up showing leaf structure, leaves, sheaths, nodes, pubescence and inflorescence.

 

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