What you’ve said is true. In my forensics class, we learned that police can actually use plants to find dead bodies, because you can see a noticeable oval of healthier plant growth. Older cemeteries flourish. There’s a few stories from the Neolithic Era about planting crops on the deceased, both humans and animals, but it’s mostly been erased from history. It wouldn’t surprise me if it’s happened during Famines or situations like the dust bowl where civilizations weren’t rotating crops and depleted the soil.