This study provides the first report that Sphagnum mendocinum (Sphagnum section Cuspidata) and S. papillosum (Sphagnum section Sphagnum) are allopolyploids. Sphagnum mendocinum is an intersectional allopolyploid, with parental species from Sphagnum sections Cuspidata and Subsecunda. It is the third intersectional alloploid species reported for Sphagnum. The gametophytically allodiploid cytotype of S. papillosum was detected in Europe, North America, and Japan. It appears to be the predominant, if not the only, cytotype for this species. Our results may warrant re-examination of the report of a haploid (n  =  x) cytotype for S. papillosum.