Phyllaries oblong or narrowly triangular, scarious margins pale to dark brown, 0.2-0.4 mm wide. Cypselae: resin gland lengths often much more than twice widths. 2n = 18, 36.

Flowering Jun-Sep. Roadsides, fields, waste places; 0-10 m; introduced; St. Pierre and Miquelon; N.B., Nfld. and Labr. (Nfld.), N.S., Que.; Calif., Maine, Mass., Pa.; Europe.

Specimens examined from inland North America that had been attributed to Tripleurospermum maritimum subsp. maritimum were all T. inodorum. The identity of the plant called T. maritimum in St. Pierre and Miquelon is uncertain; I did not have access to the voucher specimens and some plants so labeled in maritime eastern Canada were in fact T. inodorum. I am uncertain as to whether or not this taxon persists in northeastern North America. Some specimens identified to this taxon, even on the coast, may be T. inodorum individuals that have become multi-stemmed through damage or via other mechanisms, particularly on sand dunes. Such specimens are difficult to classify as annual or perennial if the taproot is not dug out, and the lack of cypselae may prevent positive identification.