These peppers are, of course, Sichuan peppercorns.

Baike says it's not conclusive if this is about [several historical figures brought up], or praising men (for fertility), or praising women (for fertility), or just about women picking peppers. Though it seems likely that the peppers are a metaphor for people and therefore the numerous fruit = descendants. This poem is a good example of the 'bixing' technique.