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Dichanthelium hirstii by Wesley M. Knapp. Image may be subject to copyright.
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Dichanthelium hirstii (Swallen) Kartesz

Hirst Brothers Panic Grass

Federal Protection: No US federal protection

State Protection: Endangered

Global Rank: G1

State Rank: S1

Element Locations Tracked in Biotics: Yes

SWAP High Priority Species (SGCN): Yes

Element Occurrences (EOs) in Georgia: 3

Habitat Summary for element in Georgia: Cypress ponds, wet savannas and sloughs


Description

Perennial grass with smooth, purplish-green stems, typically 1.8 - 3.3 feet (55 - 100 cm) tall, hairless even at the nodes. Basal rosette leaves are up to 2.8 inches (7 cm) long and 0.4 (1 cm) wide, usually smaller but always shorter and wider than the culm leaves, lance-shaped, hairless. Stem leaves 1.8 - 5.5 inches (4.5 - 14 cm) long, longest at mid-stem and 3.5 - 6 mm wide near the base of the blade, narrowly lance-shaped with long-tapering tips, erect, purple-tinged, smooth except for hairy collars and ligules. Leaves on spring-flowering stems are up to 5.5 inches long and 0.2 inch wide (4.5 - 14 cm long, 3 - 5.5 mm wide), erect, flat, inrolled only at the tips; leaves on the fall-flowering stems are erect and strongly inrolled along the margins. The base of the stem leaf forms a sheath around the stem; on the inside of the sheath, at the junction with the leaf blade, there is a narrow band of tiny hairs (ligule). The flowering spike is 2.8 - 3.5 inches (7 - 9 cm) long, less than 0.2 inch wide, with short, roughened, twisted, stiffly erect, thread-like branches. Spring flowers (spikelets) are held at branch tips, and are hairless, oval with a blunt tip, strongly ribbed, enclosed in a series of tiny bracts (glumes and lemmas). Early fall spikelets are similar to spring flowers; later in the fall, spikelets are mostly or entirely hidden inside the leaf sheaths; these two flowering phases often overlap.

Similar Species

There are nearly 50 witch-grass (Dichanthelium) species in Georgia; positive identification depends on an understanding of the technical terms for grass flowers and fruits, and on magnification by a 10x or 20x lens. Hirst Brothers’ Panic Grass is best distinguished by its pond habitat, overall lack of hairs except for the ligule and leaf collar; narrow flowering spike with stiffly erect branches; hairless, blunt spikelets; purplish-green stems; and late fall-flowering spikelets hidden in the leaf sheaths.

Hirst Brothers’ Panic Grass superficially resembles Maiden-cane (Panicum hemitomon, synonym Hymenachne hemitomon) which grows in similar habitats. It has larger leaf blades 3 - 14 inches (8 - 35 cm) long and 0.2 - 0.6 inch (0.5 - 1.5 cm) wide, inflorescences 4 - 12 inches (10 - 30 cm) long, and pointed spikelets about 0.2 inch long (2.0 - 2.8 mm) long.

Related Rare Species

None in Georgia.

Habitat

Sandy, peaty, or mucky areas within limesink, cypress, and flatwoods ponds dominated by other grasses and sedges with a surrounding fringe of Pond Cypress, Slash Pine, Red Maple, and Ash.

Life History

Named in honor of two brothers, Frank and Robert Hirst, who discovered this species in New Jersey, Hirst Brothers Witch Grass is a perennial grass that reproduces sexually. It overwinters as a low, leafy rosette and then flowers at two separate times, in the late spring and then again in the fall. Its flowers are wind-pollinated, and its seeds are probably dispersed by both gravity and small animals. The seeds apparently persist for a long time in the soil seed bank, waiting for favorable hydrological conditions. More than two years of high water will kill the plants, but seeds survive in the soil seed bank and germinate when water levels subside. The plants depend on occasional fire to kill competing woody species and to maintain an open, grassy habitat around pond edges.

Survey Recommendations

Surveys are best conducted during the two flowering periods, May–June and late August–frost, depending on rainfall, keeping in mind that the fall flowering period has two phases. Population sizes fluctuate depending on water levels, and plants may not be present every year.

Range

Currently known from 1 population in Georgia, 2 in North Carolina, 1 in Delaware, and 4 in New Jersey; there are likely fewer than 1000 plants in existence. Georgia's population, the largest known, was re-discovered in southwest Georgia in 2014, after not being seen for 67 years.

Threats

Ditching, draining, and filling wetlands; construction of firebreaks around ponds; fire suppression; conversion of habitat to pastures, pine plantations, and agriculture.

Georgia Conservation Status

Dichanthelium hirstii is ranked S1 by the Georgia Department of Natural Resources, indicating that the species is critically imperiled in Georgia. It is listed as Endangered by the State of Georgia, and is under consideration for federal listing as of 2020. Three populations were known before 1960, all on private land, but none had been seen till 2014. Because plants are inconspicuous and hard to identify, and are not visible every year, there may be undiscovered populations.

Conservation Management Recommendations

Avoid draining and ditching isolated wetlands. Protect isolated wetlands from polluted runoff from surrounding fields and pine plantations. Allow fires in surrounding uplands to burn into the edges of ponds. Avoid placing firebreaks and roads around ponds.

References

Black, J. 2019. Native Plant of the Year 2019: Hirst's panic grass – Dichanthelium hirstii. Native Plant Society of New Jersey. http://www.npsnj.org/articles/threatened_plants_hirsts_panicgrasss_dichanthelium_hirstii.html

Chafin, L.G. 2007. Field guide to the rare plants of Georgia. State Botanical Garden of Georgia and University of Georgia Press, Athens.

Flora of New Jersey Project. 2014. Dichanthelium hirstii (Swallen) Kartesz. https://www.njflora.org/2015/01/dichanthelium-hirstii-swallen-kartesz/

GADNR. 2020. Element occurrence records for Dichanthelium hirstii. Georgia Department of Natural Resources, Wildlife Resources Division, Social Circle, Georgia.

LeBlond, R.J, A.S. Weakley, R.W. Freckmann, R.F.C. Naczi, K.S. Walz, and W.A. McAvoy. 2017. Taxonomy of Dichanthelium hirstii (Poaceae), a very rare and disjunct witch-grass of the eastern U.S. Journal of the Botanical Research Institute of Texas 11(2):413-417. https://www.jstor.org/stable/44858871

McAvoy, W.A., T.S. Patrick, and L.M. Kruse. 2015. Rediscovery of Dichanthelium hirstii (Poaceae) in Georgia. Phytoneuron 2015-7:1-8. http://www.wrc.udel.edu/wp-content/heritage/Literature/Rediscovery%20of%20Dichanthelium%20hirstii%20(Poaceae)%20in%20Georgia.pdf

NatureServe. 2019. Dichanthelium hirstii comprehensive report. NatureServe Explorer. Arlington, Virginia. http://explorer.natureserve.org/servlet/NatureServe?searchName=Dichanthelium%20hirstii

Patrick, T.S., J.R. Allison, and G.A. Krakow. 1995. Protected plants of Georgia. Georgia Department of Natural Resources, Natural Heritage Program, Social Circle.

Schuyler, A.E. 1996. Taxonomic status of Panicum hirstii Swallen. Bartonia 59: 95-96. https://www.jstor.org/stable/41610049?seq=1#metadata_info_tab_contents

Swallen, J.R. 1961. A new species of Panicum from New Jersey. Rhodora 63: 235-236. https://www.jstor.org/stable/23306280?seq=1#metadata_info_tab_contents

USFWS. 2016. Hirst Brothers’ Panic Grass (Dichanthelium [Panicum] hirstii) [evaluated for listing]. U.S. Fish and Wildlife Service, New Jersey. https://www.fws.gov/northeast/njfieldoffice/endangered/hirsts.html

Walz, K.S. 2012. The legacy of Hirst Brothers' Panic Grass. U.S. Fish and Wildlife Service. https://www.fws.gov/endangered/news/episodes/bu-11-2012/story4/

Weakley, A.S. 2015. Flora of the southern and mid-Atlantic States. University of North Carolina Herbarium, University of North Carolina, Chapel Hill. http://www.herbarium.unc.edu/flora.htm

Authors of Account

Linda G. Chafin

Date Compiled or Updated

L. Chafin, Feb. 2007: original account.

K. Owers, Jan. 2010: updated status and ranks, added pictures.

L. Chafin, Feb 2020: updated original account.

Dichanthelium hirstii, illustration by Jean C. Putnam Hancock. Image may be subject to copyright.
Dichanthelium hirstii by Wesley M. Knapp. Image may be subject to copyright.
Dichanthelium hirstii. Image may be subject to copyright.