From 2speccers2tools wiki

The stacknom arose when radfauna, in the form of the oof mamal, had made it to Oofle and began irradiating things, a mutated nomweed had its bottom duplicated, which not only gave it more leaves, but also 3 hearts in total, the extra water intake these organs require to not be running dry has however driven it to the moister coast, and actually have been a large detriment thus far, the stacknom is lucky that not much other blue flora actually lives on the coast and thus it has probably a while to figure things out even if it's all messed up.