Friends often hear me say that weeds are really wildflowers. In fact, every spring I anticipate the emergence of the dainty wild violets, purple dead nettle, henbit, and buttercups, even the dandelions, which provide the first food available for the honeybees.

Weeds often are defined as “plants out of place,” but weeds also can cause economic losses when they overwhelm vegetable gardens. Invasive weeds like English ivy and Japanese stiltgrass cause environmental damage by crowding out native habitat and food sources for insects, birds, and small mammals. Toxic weeds like giant hogweed and water hemlock pose serious health hazards for humans and animals.

By early summer, my enthusiasm for green things I didn’t plant wanes, and I despair of removing the blasted weeds from the flowerbeds. Weed removal is an ongoing chore for the gardener and an uphill climb for the property owner who maintains turfgrass, a problem we don’t have. The green space around our house is about 5% grass, 5...