Thanks!
Hmm, so the composter (the bucket you mentioned) can’t be picked up, only interacted with. When you pull up a weed it gets added to the resource tracked in the top right corner, and then interacting with a composter will process those and turn them into fertilizer items, which can then be picked up and activated on the pumpkin.
As for the platforms, you can only place them on the pumpkin, and only above ground level. When the pumpkin is bigger, try jumping and then pressing “C” (or “L”).