If you are thinking of Football Mums, they start with special late flowering varieties, and are made even bigger with an exacting training method. The plants are started with vigorous young cuttings, and tied to a strong stake as they grow, commonly in a greenhouse, to extend the growing season. The plants are pampered with constant watering and frequent, light feeding. Every time the plants branch, the strongest branch is tied to the stake, and all the others are pinched out. When the flower buds form, all but one of the buds on the plant are pinched out, and that one grows to become the huge pompon sold in the flower shops in fall.