Pinch out the center leaves on marigold seedlings to encourage dense growth. New leaves form in the node between the branch and the main stem, creating a new set of branches. Pinch the center leaves from the new branches in approximately three weeks to encourage further branching.
Deadhead marigold blooms by clipping or pinching the stem just behind the bloom as soon as the flowers begin to fade. This sends a message to the plant that it has not produced enough blooms to form adequate seed for reproduction. To compensate, the plant produces new blooms.
Trim the entire plant back by one-third of its growth when it shows reduced growth and vigor. A few day's neglect during hot, dry periods can leave marigolds with reduced or shriveled blooms. Cutting them back to healthy growth revitalizes the entire plant.