Familiar as corsages and potted gift plants, chrysanthemums are the iconic fall bloomer. Available in a wide range of colors, from white through yellows to reds, pinks and purples, there is a shade for every garden. Orange, russet and gold are particularly appropriate for this time of year. Bicolors are particularly striking.
Forms vary just as much. Spider mums have long petals forming shaggy heads, while others resemble simple daisies. Most garden mums have double blooms such as the one pictured at left. All in all, the US National Chrysanthemum Society recognizes thirteen bloom types. The flowers are supported by stiff stems approximately two feet high and adorned with elongated heart-shaped gray-green leaves with uneven edges.
Chrysanthemums are easy to grow, both in containers and in a perennial border. Set out transplants or divide existing plants in late May. Full sun increases bloom and reduces the likelihood of powdery mildew on the leaves. Mums appreciate well-drained soil amended with compost and a time-release fertilizer. (In a container, use a commercial soilless potting mix.) Irrigate to keep a bit moist, but don’t let their roots sit in a puddle. And remember, mulch is always a good idea. Once cold weather has killed the top growth, an additional eight inch layer of fluffy mulch or evergreen branches will help these USDA Zone 5 perennials survive the winter, especially in colder areas.
Pinching the ends off of the growing stems encourages branching, keeps plants compact, and increases the number of flowers. Stop once summer arrives, however, so that flowers have a chance to bloom before the snow flies.
Mums are susceptible to a variety of insects and diseases, including Verticillium wilt, septoria leaf spot, spider mites, aphids, leafhoppers, leafminers, and the above-mentioned powdery mildew. Be sure the problem is correctly diagnosed before reaching for any pesticides.
Excellent border perennials, chrysanthemums also do well in containers where they can be moved to center stage during their season of bloom season. Companion plants might include sedums, ornamental grasses, and dwarf evergreens as well as other perennials.
Article and photos by Leslie Holzmann, Colorado Master Gardener.