Most of us don’t think about our garden mums until they brighten our gardens late in the growing season. But to get the best display of flowers this fall, you should pinch the plants back to create more branching and more flowers.
Mum plants flower in response to both day length and temperature. Most cultivars begin to develop flower buds when days are less than 12 hours long and generally continue to flower for a period of 6-8 weeks. Some cultivars are not as responsive to day length and may begin flower development early in the summer in response to heat, especially if they have not been pinched back. Catalogs usually list cultivars as early, mid-season or late types.
For established plants, simply remove about one-half to 1 inch of stem back to a leaf, using floral scissors or hand-held pruning shears. The first pinching should be done when the plants are about 6 inches tall (about mid-June in central Indiana) to induce lateral branches. As soon as these lateral branches become 6 to 8 inches long (about mid-July), they, in turn, should have their tips removed to induce more branching. This procedure may seem drastic, but the results will be bushy, well-shaped flowering plants. After the July pinch, let the plants’ foliage take its course–pinching too late can reduce the number of flower buds.
Plants purchased this summer and fall have likely been groomed to have a compact habit that is loaded with flower buds. But in order to recreate that affect next year, you’ll need to do a little pinching next spring and summer to promote branching.