READ BELOW:
Greenhouse:
First time you visit Greselda's Castle, it unlocks "Create Dark Seeds".
Note from maguar - I unlocked this after Garden Ceremony and before I collected from Greselda
Second time you visit Greselda's Castle, it unlocks "Grow Dark Seeds".
You need the pile of seeds, glimmer shards, & glimmer fragments to craft the "Create Dark Seeds" in the Greenhouse.
When the "Grow Dark Seeds" is unlocked after
visiting Greselda's Castle twice, you need those dark seeds, water & fertilizer to craft the glimmer plants required to upgrade
the Maze Garden to level 2.
2nd post on the first page of this thread is very helpful for checking your progress. You can refer to it repeatedly to check that progress.
To upgrade the maze to level 2:
The faerie bulb seeds are used to craft useless items you can get easier by other means. So no need to worry about harvesting them at all!