This species can be difficult to separate from the northern and southern spreadwings (see those species for discussion of difficulties). The male's thorax is blackish above with pale shoulder stripes and pale tan to blue-gray sides. Often there are small dark spots on lower sides of the thorax. The abdomen is blackish above with a pale gray tip when mature. The colors are obscured by pruinosity as the spreadwings age, especially in males. The male is usually elongated with the female more sturdy. The female's thorax is blackish above with pale shoulder stripes. The female has a long ovipositor that extends to and sometimes beyond the tip of segment 10 (see photo). The abdomen is blackish above as well. The northern, southern and lyre-tipped spreadwings are very similar to the sweetflag spreadwing in appearance. The body length varies from 1.3 to 1.7 inches. Both genders often have a pale brown spot on lower sides of the thorax like the spotted spreadwing, but paler.
The sweetflag spreadwing is usually found at temporary and permanent ponds, marshy lakes, and slow streams. It ranges throughout eastern United States and southeastern Canada. It is occasionally found in scattered northern counties in Wisconsin. However, it is difficult to separate from the northern spreadwing and southern spreadwing, and because survey effort for spreadwings in Wisconsin has been generally inadequate, its distribution in the state is poorly known.
Mid-July to early September in Wisconsin.