hmm this is complex but all of what im gunna say is based on what i think and it may be right or wrong but here goes
kaede wanted to turn earth back into what it was, or purify it because she said that earth was crying. she wanted to turn everyone into plants, including the arigami into plants so that everyone could be happy and mother earth would be happy. thats why if you remember kusanagi was being healed, momiji sensed him getting weaker and that kaede wanted him to return to earth, since arigami of course are plants. susano was supposed to be the god of all the arigami, but he fitted in by that he was actually created by the kushinada blood line to help mentally controll the plants or arigami i suppose. marakumo thought that with the help of susano and kaede they would turn everything to plant creatures so it would be an all plant kingdom, but realized that kaede didnt plan that at all, but planned everything would turn into simple plants. the seeds coming from the plants changed because momiji did the rite of matsuri ( ithink thats how ya spell it) which made every coexist or live with nature thats why during matsuri everyone felt happy and warm and ran out to celebrate. cause in the series we find out why momiji and kaede were born twins, momiji did the right and proper matsuri without having everyone turn into plants that kaede wanted.
whew that was long, hopefully thatll help somehow
