Plants growing in arctic North America and those in extremely wet habitats, such as bogs, often have a different superficial appearance. The leaves are straight, erect, ovate-lanceolate, short-acuminate with weak serrations on the margins, and the abaxial ridges on the costae are poorly developed. Sometimes the plants have distal shoots with abnormal appearing leaves that are shorter and broader than those below. Some of these collections have been referred to Dicranum latifolium, which I consider to be a synonym of D. scoparium. Further field and laboratory studies are required to clarify the taxonomic status of those plants. In the sterile state, large-leaved plants of D. scoparium can be confused with D. majus. The latter is immediately distinguished by a double row of guide cells, instead of the single row in the former, thicker stereid bands, distal cells that are narrower and more elongate and costae that have small teeth or serrulations distally on the abaxial surface instead of the characteristic 2-4 toothed ridges of D. scoparium. When fruiting, the solitary, rarely paired, sporophytes of D. scoparium distinguish it from D. majus, which has multiple sporophytes, 2-5 per perichaetium.
- Flora of North America @ eFloras.org