How to Grow Chrysanthemums
Chrysanthemums make wonderful fillers in fall gardens. Pair with pumpkins, cornstalks, and other fall-holiday motifs. Select from autumn colors such as brown, red, orange, and yellow. Also available are pinks, whites, lavenders, and purples. Use these as specimens or en masse for a big show of easy color. Remove spent flowers to encourage fresh bud opening and a longer season.
In the Lower and Coastal South, choose a spot with shade from afternoon sun. Don't plant near large trees or hedges with invasive roots. Set out young plants in early spring. Plant in well-drained garden soil improved with organic matter and a complete fertilizer dug in 2 to 3 weeks before planting.
Water deeply at intervals determined by your soil structure—frequently in porous soils, less often in heavy soils. Too little water causes woody stems and loss of lower leaves; overwatering causes leaves to yellow, then blacken and drop.
Feed plants in ground two or three times during the growing season; make last application with low-nitrogen fertilizer not less than 2 weeks before bloom.
Aphids are the only notable pest in all areas. To avoid them, feed plants with a systemic insecticide/fertilizer combination, or spray with horticultural oil or insecticidal soap.
To produce sturdy plants with big flowers, start pinching at planting time by removing plant tip. When lateral shoots form, select one to four shoots for continued growth. Keep pinching all summer, nipping top pair of leaves on every shoot that reaches 5 in. long. (Stop pinching earlier in coldest regions). For huge blooms (on large-flowered sorts), disbud (remove all flower buds except one or two per cluster). Stake plants to keep them upright.
Sometimes mums are fooled by cool weather and short days into blooming in spring. After they flower, cut them back to within 8 in. of the ground; they'll bloom again in fall. (However, any mum that blooms prematurely in late summer isn't going to bloom again that year, even if you do cut it back.) After fall bloom, cut plants back to 8 in.; where soils are heavy and likely to remain wet in winter, dig clumps with soil intact and set them on top of the ground in an inconspicuous place. Cover with sand or sawdust, if you wish.
Take cuttings from early to late spring (up until May for some types), or when shoots are 3–4 in. long. As new shoots develop, you can make additional cuttings of them. Or you can divide older clumps; take divisions from the outside and discard the woody centers.
Growing in Pots
Pot rooted cuttings any time from February to April, using porous, fibrous, moisture-holding planting mix. Move plants to larger pots as growth requires—don't let them become root bound. Pinch and stake as directed above. Plants need water daily in warm weather, every other day in cool conditions. Feed with liquid fertilizer every 7 to 10 days until buds show color.