Vascular Plants of North Carolina

Account for Grassy Arrowhead - Sagittaria graminea Michaux

Section 5 » Order Alismatales » Family Alismataceae

Author	Michaux
Distribution	Scattered over the Sandhills and eastward to the Croatan National Forest area (Craven/Jones/Carteret counties) and southward. However, it is likely to be found elsewhere in the Coastal Plain north of Moore and Craven counties. Specimen records from a number of other counties have been annotated to S. chapmanii and S. weatherbiana. Thus, bona-fide specimens of graminea are much less numerous than references might suggest. This species has a very wide, yet extremely spotty, range across the eastern half of the continent. It ranges from eastern Canada south to the Gulf Coast. Note that the BONAP map may well include one or two additional taxa that have been pulled out as species by other entities.
Abundance	Infrequent to rare, but easily overlooked due to its grass-like appearance when not in bloom. The NCNHP added this species to its Watch List (W7) in late 2022.
Habitat	This species favors standing shallow water, such as pool and pond margins, margins of impoundments, edges of tidal freshwater marshes, and at inland marsh edges.
Phenology	Blooms from May into November, and fruits shortly after flowering.
Identification	This is a very slender and mostly grass-like Sagittaria, and lacks arrowhead lobes. Like a few other species, the growth form differs greatly as to whether it grows submerged or emerged. Most plants are emergent, with leaves reaching up to 1 foot tall, and with the upper third being the blade, which is usually quite narrowly elliptic, less than 1/2-inch wide. However, submerged leaves can be longer and very slender, strap-like, with the leaf not showing an obvious blade. The flowering stalk is variable in length, but averages perhaps 10 inches high, with 2-12 whorls of white flowers; flowers are white with 3 petals and can be as much as 1 inch across -- fairly large for the size of the plant. The very rare S. chapmanii has the inflorescence branched at the base (as a panicle) as opposed to unbranched in this species (and most others in the genus). The other rather similar plant, with narrow (but not linear) leaf blades, is S. weatherbiana, which is a larger plant and has the leaf blades mainly 1/2-1-inch wide and also with the blade rounded at the tip and not acute as in these other two species. An often overlooked but very helpful character of Grassy Arrowhead is the thick and hard, short rhizome, absent in its relatives.
Taxonomic Comments	Though this has long been a good species, a number of other taxa have been included within it that Weakley (2018) and some others consider as valid now. These include S. weatherbiana and S. platyphylla, each considered by RAB (1968) as varieties of graminea.
Other Common Name(s)	Grassleaf Arrowhead, Grass-leaved Arrowhead
State Rank	S2S3
Global Rank	G5
State Status	W7
US Status
USACE-agcp	OBL link
USACE-emp	OBL link

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