How do ferns reproduce without seeds?

Ferns reproduce through a process called alternation of generations, which involves two distinct life stages: the sporophyte and the gametophyte.1

The familiar fern plant is the sporophyte. It produces spores within specialized structures called sporangia, which are often clustered in groups known as sori on the undersides of the leaves. Once released, these spores are dispersed by the wind.231

If a spore lands in a suitable environment, it germinates into a tiny, heart-shaped sexual plant called a prothallium (the gametophyte). This structure produces sperm and eggs in organs called antheridia and archegonia. Fertilization occurs when sperm swim through water to reach an egg. The resulting zygote then develops into a new, independent sporophyte, eventually causing the prothallium to wither and die.231

Additionally, some ferns can reproduce vegetatively through their rhizomes or leaf proliferations, and many species are apomictic, allowing them to produce new sporophytes directly from gametophyte cells without fertilization.2