You've pinched, watered and deadheaded and been rewarded with a smoky cloud of blooms on your garden chrysanthemum (Chrysanthemum morifolium). If you garden within the plant's hardiness range, United States Department of Agriculture plant hardiness zones 5 through 9, you can enjoy its late-season beauty again next fall -- with a bit of further grooming and a protective mulch.
Late Summer Care
Chrysanthemums are long day-short day plants, meaning they need the long days of summer to initiate flower buds and the shorter days of fall to cue blooming. Other chrysanthemums such as the florist's chrysanthemums (_Chrysanthemum indicum_), are less hardy or need longer to flower than all but greenhouse culture offers. They are hardy in USDA zones 7 through 12 but grow in all zones as annuals. The garden chrysanthemum offers hardy varieties that bloom in early to late fall.
Wherever you live, water chrysanthemums during dry periods of fall into winter until the ground freezes. Fertilize chrysanthemums only until midsummer -- late fertilization encourages vulnerable new, green growth. Use a water-soluble 20-20-20 blend mixed at the rate of 1 teaspoon per 1 gallon of water and apply ever other week.
Early Fall Care
In colder zones, chrysanthemums die back after the first hard freeze in October, but in warmer zones, they may bloom long enough to provide flowers for a holiday arrangements, so plan cleanup by freeze dates rather than season name.
Pinch fading blooms with thumb and forefinger to keep blooms coming and plants bushy. For larger blooms, pinch off side buds on the same stem. Add water, if necessary, to total 1 inch of water a week with rain to keep plants producing blooms.
When the End Comes
When the ground freezes, cut the chrysanthemum back a few inches just to tidy up the plant and remove clippings. In warmer climates, cut the plant back to leave just 2 to3 inches of stem when the ground freezes. Sink potted plants in the ground, heel into a cold frame, or wrap and store in an unheated garage or shed.
New plants start up on roots of the old -- you'll see the distinctive green leaves in tiny rosettes around the stem. Protect them with a 3-the to 5-inch layer of pine straw or other clean organic mulch. You'll be rewarded with baby plants in spring. Sever them from the parent with a sharp spade to increase the collection. Remove the mulch in late winter or early spring just before the last frost date to harden off these young plants.
Success and Failure
- Garden chrysanthemums differ in hardiness, from the rugged button and cushion mums to the less reliable fancy varieties. Extreme weather can kill hardy plants in zone 5. On the other hand, zone 9 gardens that remain unfrozen may see almost continuous growth of new plants -- but lack of chilling may result in short-lived baby plants. Learn what type of plant does best in your area for best success in overwintering.