Really really want this. Gardening is one of my favorite things to play with in TS and honestly, I really miss compost bins in TS4. I wish they'd rework how fertilizers work in the game and add proper composting to TS4. It's really bizarre to me how sims in 4 can fertilize plants with any harvestable or fish without them being decomposed.
Lawn mowers and compost bins would go very well together, sims could use the weeds from the lawn mower or by pulling them manually in the bins to create compost to use as fertilizer. With Seasons sims should be able to put the piles of leaves in the compost bins to make fertilizer too.