Aka orbees. Also useful as a soil amendment if you have clay soil, it stops it from claying so much and retains water underground for plants.
They make glow in the dark ones, which I put into a masonry jar with some distilled water and a drop of bleach, I light it from underneath with a USB LED and it glows for about an hour. Cool night time light.
Back in the early 90s they had a different name and they were irregularly shaped. This was for Soil Amendment. I think it started with a Z.
> I think it started with a Z.
i don't think so. It was a brand name of whatever SAP they had decided was safe for plants to bathe in. I found some about a decade ago, just by asking about water retention crystals at an agricultural outlet. I think it's cheaper to buy orbees when they're on clearance, though.