It is better to buy a plant with many partially opened buds since it will have a longer period of bloom than a plant in full bloom. The chrysanthemums you plant this fall will carry over the winter and resume growing in the spring. Failure to divide the clumps will cause weak, spindly growth with few flowers. Select strong-growing clumps and separate the individual shoots with an adequate root system, so the new small plant can become reestablished quickly. Avoid using the shoots in the center of the clump because a crown rot fungus, which may weaken or kill the young plants, is often present.
Chrysanthemums grow best in well-drained soil.
The yearly addition of compost or other suitable organic matter to the planting bed is desirable. The plants should be set 18 to 24 apart to provide adequate space for development. Vigorous varieties may need a 30-inch spacing to prevent crowding. After the plants are established and at least six inches tall, pinch off the top one to two inches of the stem. This will encourage lateral branching and produce lower, bushier plants.