Sacks was talking about the restorative power of gardens. Of being in nature. That it offered powerful medicine to the brain.
He said that of his neurology patients, even those whose minds were far gone with Alzheimer’s: if you got down to the soil with them and handed them a seedling, not one, ever, had tried to plant it upside down.
They knew how these things must go, and the worst ravages of the brain could not take that away from them.