Swamps (both cedar and deciduous) and stream banks; mixed forests, especially at borders, as on bluffs along Lake Superior.
Specimens of S. decora with more prolonged acute apices on the leaflets than is often the case are frequently misidentified as S. americana if one is not familiar with the overall lanceolate, longer leaflets of the latter species (usually ca. 4 times as long as broad). Checking several representative leaflets in case of doubt should be sufficient to decide on which side of the length-width ratio a specimen belongs (3.2 apparently is a nearly certain dividing line, as indicated in the key).
MICHIGAN FLORA ONLINE. A. A. Reznicek, E. G. Voss, & B. S. Walters. February 2011. University of Michigan. Web. April 23, 2019. https://www.michiganflora.net/species.aspx?id=2569.