Spartina

1. Plants wiry, with slender culms ca. 1–1.5 mm in diameter and 25–60 cm tall; spikes 1.5–3.5 (–4.5) cm long; rhizomes 1.5–3 mm thick; anthers ca. 2.5–3.5 mm long.

S. patens

1. Plants more robust, culms 1.5–11 mm in diameter and (50–) 60–200 cm tall; spikes (3–) 4–12 (–15) cm long; rhizomes (2.5–) 3–8 mm thick.

2. Glumes awnless or at most short-mucronate, spikes tightly appressed to the rachis at maturity.

S. gracilis

2. Glumes (at least the longer) distinctly awned; spikes somewhat spreading at maturity.

S. pectinata

All species found in Spartina

Spartina gracilisALKALI CORDGRASS 
Spartina patensSALT-MEADOW CORDGRASS 
Spartina pectinataCORDGRASS 

Citation:

MICHIGAN FLORA ONLINE. A. A. Reznicek, E. G. Voss, & B. S. Walters. February 2011. University of Michigan. Web. August 21, 2017. http://michiganflora.net/genus.aspx?id=Spartina.