View Rhonda Ferree's MUM YouTube video athttp://go.illinois.edu/ferreevideos
Have you ever had a fall blooming mum that doesn't look at all like what it is supposed to come September? Is it tall, leggy and flopping over with a few flowers at each stem tip instead of short, compact and full of flowers? Pinching at the right time is the answer. Martha Smith, Extension Educator in Horticulture at the Macomb Extension Center offers the following information about pinching mums.
Depending on what book you refer to, fall blooming mums are listed as Chrysanthemum X morifolium or Dendranthema X morifolium. Whichever way they are listed, their flowering is a response to shorter daylength and their size is controlled by hormones within the plant. What gardeners need to understand with these fall bloomers is a simple form of pruning called pinching. We control both flowering and height with pinching.
Pinching, very simply, is the removal of the growing tips and about 2 to 3-inches of growth. You can do this by hand or cutting back the growth with pruning shears.
Why do we do this? Mums are short day plants. Their flowering responds to shorter day length. In spring and early summer, our length of daylight is longer so the plants only produce vegetative growth. As fall approaches and day length shortens, their flowering response is triggered and they set buds.
Size is controlled by hormone dominance in the plant. In spring, each growing tip is dominant over the lower side buds along its stem. As long as the tip bud is present, the side buds won't break and branch out. You have to break the hormone dominance by removing the tip. Once this is done, the side buds will break and branch out. An unpinched plant results in a leggy plant that flops over. A pinched plant remains shorter producing tight, compact growth. Now as the plant continues growing, all of the new growing tips are dominant, so we pinch a second time. The first pinch is in spring when returning plants are about 8 to 10-inches tall. If you are planting mums in the spring, start the first pinch 2-weeks after planting. The second pinch is done around the summer solstice. This is the longest day of the year. Day length is shorter after that and the plants will naturally set buds. Many gardeners plan their final pinch on or about the 4th of July.
You now have a compact plant that will set buds and bloom according to its internal schedule. Mums need several weeks after the final pinch to set buds. Early blooming mums set buds more quickly than later blooming mums. Experiment. Mark in your garden journal the pinch dates and when the mums flower. If you want later bloom, your #2 pinch could be delayed 1-2 weeks, or add a third pinch. If you want a tighter, more compact plant, take more plant stem when you pinch, or add a third pinch.
Enjoy your fall garden mums. Ornamental grasses such as Miscanthus 'Morning Light" or "Malapartus", fall blooming aster "Purple Dome' or "Monch" and goldenrod "Fireworks" all are wonderful companion plants for your fall garden.Source: Martha A. Smith, Horticulture Educator, University of Illinois Extension