I'm sure my grandparents never heard of Miracle-Gro. To them, "miracle grow" meant their gardens survived the drought and grasshoppers of the 1930s and yielded enough food to store through winter.

If you could see within a cluster of daffodils or a lemon tree, you’d discover an intricate mechanism unfurling under the soil. The soil or the potting mix, which appears as a crumbly cake, hides ...