Chrysanthemums are just about the easiest of all of the perennials to grow. They should be planted in early spring after all danger of freezing, however they can be planted almost any time, as long as they have time to establish their root system before the hottest weather. They grow best and produce the most flowers if planted in full sunshine, and respond to plenty of food and moisture.
There are hundreds of varieties of Chrysanthemums, giving you the options of height, color, flower size and time of bloom, so you can pick and choose to fit your needs when you visit the nursery. In northern climates it is wise to purchase the earlier bloomers.
Chrysanthemums can be started as seeds, cuttings, divisions, or purchased at a nursery as bedding plants up to gallon sized plants. they should be planted into well prepared, fertile, sandy soil. They resent "wet feet" so the hole should be dug deeply. I would recommend that you not grow your mums in the same spot for more than three consecutive years to help prevent disease and pest problems. The plants should be spaced 18-30 inches apart for best results. Feed lightly every 2 weeks with a good balanced all purpose fertilizer. When the plants are 6 inches tall, pinch about 3/4 of an inch from each branch to promote more blooms and bushier plants. When they reach a foot tall, pinch them again. On the largest flowering types it is best to remove all buds except for the one on top.
Young divisions will grow much faster and provide a better plant than crowded old clumps. When the new shoots are 1-3 inches tall in early spring, dig up your old clumps and carefully pull them apart. plant the healthy divisions into newly prepared fertile soil and discard the half dead woody parts.
Strip the lower half of the leaves from a 4-6 inch healthy cutting. (Using a sharp clean knife!) Dip about 3/4 inch of the cut end into a rooting hormone such as Roottone or Hormonex, and insert the cutting about one inch deep into sterile moist sand, vermiculite or sphagnum moss. Create a mini-greenhouse over the container with poly film over a wire frame and place it in a bright spot (NOT full sun) until the roots form.
Chrysanthemum seeds should be sown into the prepared soil where they are to bloom at least 2 months prior to the first frost. Seeds may also be started indoors in very early spring for later transplanting. The temperature of the rooting medium must be kept at a constant 70-75 degrees. Germination can take from 8-25 days.