Fertile stems are at first unbranched and lack chlorophyll but become branched and green after spores are released. The spores germinate to produce a distinct gametophytic generation. The establishment of gametophytes and subsequent sexual reproduction is rare in the wild due to an extremely narrow habitat tolerance. The most critical factor for sexual reproduction appears to be the initial establishment of spores. Gametophytes only establish on recently exposed bare mud, such as around resevoirs or streambanks following flooding.
Wood horsetail has a very limited spore dispersal period, and spores are short-lived.
Male gametophytes grow at a much slower rate than females. There is also evidence of early male mortality. Gametophytes reach sexual maturity at 3 to 5 weeks and then produce a constant supply of gametes until death. In the Northern Clay Belt Region, Ontario, fertile shoots of wood horsetail appear before sterile shoots, liberate their spores, and die before sterile shoots complete their growth.