Without pinching, mums will naturally bloom in mid-summer. To prevent this, you want to begin pinching the plant for every 5 inches of growth beginning in the spring through to mid-July. Then, you'll get the classic fall blooming mums.u003cbr/u003eu003cbr/u003eIf you buy potted mums, you can expect them to also bloom in the fall. For the most part, you won't even begin to see mums until the end of summer to early fall, when the plant already has buds and blooms.