Joey Williamson, Ph.D.
Home & Garden Information Center
Seeing chrysanthemums at your local garden centers is a sure sign that fall is around the corner. Mums are one of the oldest flowers in cultivation, and the modern garden mum (Dendranthema x grandiflorum) is actually a hybrid composed of many wild species from Asia. These garden mums are the most common type of mum for sale in the fall, and they come in a large variety of colors, ranging from brilliant yellows to lavenders, burnt oranges and reds, white and bronzes. In addition to the array of colors, they may be found in an assortment of interesting flower types, such as pompons, singles and cushions. As an added bonus, most garden mums are perennial in South Carolina, so they may be planted in a sunny site with well-drained soil.
Burnt Orange Garden Chrysanthemum
Joey Williamson, © 2008 HGIC, Clemson Extension
Although garden mums can be found in the spring for planting along with warm-season bedding plants, it’s nice to think that your recent purchase of the large, blooming mum can become a spectacular addition for the perennial bed. Always improve the soil with organic matter, such as compost from your own compost pile, or purchase composted manure or a composted planting mix. A soil test is highly recommended for your flower beds in order to know exactly what amount of limestone is required and the type of fertilizer to use. The best soil pH for mums in the landscape is 6.5, and most soils in South Carolina that have not been limed are sufficiently acid to require around four (4) pounds of lime mixed into 100 square feet of bed. Incorporate the recommended amount of fertilizer, but without a soil test consider mixing two pounds of an organic, slow-release fertilizer, such as a 4-6-6 into each 100 square feet of bed before planting. This will help stimulate root growth during the fall and early spring. Remember that all soils are different, and these are simply general guidelines for lime and fertilizer.
Lavender Garden Chrysanthemum
Joey Williamson, © HGIC, Clemson Extension
Trim the spent flowers from the mum and water it well prior to planting. As with most plants, do not plant the mum in the soil any deeper than it was in the container. Once planted, water it well to settle the soil, mulch with a two-inch thickness of pine needles, leaves or bark, and keep the plant moist until cooler weather arrives. The top will die back with the first frost, and at that point should be trimmed off.
New growth will appear in the spring, and once the chance of a last spring frost has passed, the mums can be fertilized. If using a slow-release fertilizer, such as a 12-6-6, mums can be fertilized on April 1 and June 1 with one pound per 100 square feet of bed each time. This will provide all the fertilizer they need through the time of flower bud formation. Water the mums well on a weekly basis if it doesn’t rain.
There is a trick to having a thick, dense plant in the fall that is not too tall or floppy - pinch back the plant during the late spring and early summer. Pinch the ends of branch terminals or prune the plant lightly on approximately May 1, June 1 and again on July 1. This will result in a very branched mum with flower clusters at the end of every branch.
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This information is supplied with the understanding that no discrimination is intended and no endorsement by the Clemson University Cooperative Extension Service is implied. All recommendations are for South Carolina conditions and may not apply to other areas. Use pesticides only according to the directions on the label. All recommendations for pesticide use are for South Carolina only and were legal at the time of publication, but the status of registration and use patterns are subject to change by action of state and federal regulatory agencies. Follow all directions, precautions and restrictions that are listed.