A traditional African staple that is now a global crop, peanuts are legumes that literally plant themselves. As soon as the small ground-hugging flower dies, a spike will elongate and descend into the soil, where the peanut will grow in the safety of the roots of the mother plant.
To harvest, wait until the plant has almost completely died back and then lift with a fork. The precious peanuts will be hanging in clusters beneath the plant.