Mums are everywhere in autumn. Yellow, orange and even burgundy mums in containers fill the shelves of garden stores in September, their blossoms so lovely and varied it's tempting to walk out with half a dozen pots balanced precariously in your arms. Mums (Chrysanthemum spp, or Dendranthema x grandiflora) are usually hardy perennials that survive chilly winters if planted in spring. Mums purchased in fall are usually destined for the compost bin when flowering is done, although -- with sufficient nurturing -- they can sometimes make it through the winter.
In Fall, Mum's the Word
In the perfect garden scenario, you would buy potted mums in early spring, plant them in spring, nurture them all summer and enjoy their blooms in autumn in U.S. Department of Agriculture plant hardiness zones 3 through 9. Garden centers tend to offer mums in fall, however, because the bright, compact petals of the blossoms catch the eyes and heart of gardeners in a way the foliage simply does not. Mums are sold in fall because they are about to bloom, and some people treat them as extended-life cut flowers, either keeping the plants in the containers or transplanting them to garden beds intending to toss them when the pretty flowers wilt.
If this is your intention, caring for fall mums is not difficult. Buy color combinations that please you and work well with other plants. Place the pots in the sun or, if you are transplanting, put the plants in a sunny location in well-draining soil. Keep the soil constantly damp without letting it get waterlogged. Dig down into it a little with your fingertips regularly to evaluate whether the plants need water. Do this each day during warm spells and every other day when the weather turns cooler. Don't fertilize at all or worry about pests because the plant's life will be short. Simply snip off wilted flower heads with a garden pruner, sterilizing the cutting surface first by soaking in a mixture of 1 part water and 1 part denatured alcohol.
Keeping those Mums Alive
If you decide to try to keep fall container mums alive over the winter, you have two choices. You can either plant them in the ground with winter protection or you can overwinter them in your garage or basement.
If you decide to plant them in the garden in fall, get the mums in the ground in well-draining soil as early in fall as you can, spacing them 18 to 24 inches apart. You want to give them as much time as possible to establish root systems that will help them survive. Keep the soil moist. Once the foliage is killed by several hard frosts, cut the stems to 1 inch long. Cover the plant with a 3- to 4-inch layer of light mulch -- like pine needles or straw -- to keep the soil from freezing.
If you keep the mums in the container they came in, wait until the foliage browns, then give the plant a serious haircut, snipping off the stems to 1 inch long. Do not forget to sterilize pruners before clipping. Move the container to a sheltered spot outdoors or inside where it will be protected. In warmer climates you can leave it outside, but move it under a tree or against a wall to cut the wind, and cover the plant with about 8 inches of light mulch or dried leaves. In colder climates, bring the pot into a garage or basement, using newspapers beneath it to protect its roots from cold, and wrapping the pot in newspapers too. Indoors pots need water when the soil dries out, so check moisture every week.
If the plants make it through winter, you will begin to see new growth in March or April. Begin fertilizing with a water-soluble, all-purpose fertilizer, such as a 10-15-10. Add 7 drops to every quart of water you offer the plants.