I gave the kids a patch of soil where in years past we have planted a garden. This year, we only managed to plant in the pots on our deck, so this patch by the garage was just sitting there filling with weeds.
I provided them with a few garden tools and a small garden play kit from the dollar store that included a watering can and some plastic gardening tools. I also lay out some gloves and packets of seeds. I gave them no direction whatsoever except to point out to the older ones that on the packets of seeds, it lists how deep they should be planted and how far apart. I then set them loose in this gigantic sensory bin to do as they pleased!
It was a bit of a challenge for me not to want to give them instructions or show them how to plant so I had to consciously step back and let them explore. I was there if they wanted to ask questions but I let them just have fun and do things the way they wanted to. Some of them ditched the tools after awhile to get in there with their hands and really get muddy once they had poured water in there!
They especially liked that I gave them real seeds to plant. I imagine we may have some surprise vegetables popping up in a few weeks!
If you are looking for information on making sensory bins, you may be interested in my book.