Pinch those Mums!
This article was originally published on June 28, 2017 and expired on July 30, 2017. It is provided here for archival purposes and may contain dated information.
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 being short, compact and full of flowers? Pinching at the right time is the answer.
Depending on what book you refer to, fall blooming mums are listed as Chrysanthemum or Dendranthema species. 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 flowering, height and overall shape with pinching.
Pinching, very simply, is the removal of the growing tips and about 2 to 3-inches of growth. (Do not cut all the way back to the ground) You can do this by hand or cutting back the growth with pruning shears. Debates rage as to which method is preferred by the plant! Either way, you can shape the plant as you go. Mums are short day plants. Bud set occurs when we have warm days with short day length. In spring and early summer, temperatures are warming up and days are getting longer. As fall approaches temperatures are warmer and day length shortens. The flowering response is triggered and mums set buds.
Size and shape are 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, branched growth. Now as the plant continues growing, all of these new growing tips are dominant, so we pinch a second time. The first pinch is in spring when 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 second 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 but make sure you leave enough of the stem with buds present.
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 blooming mums.
Source: Martha A. Smith, Extension Educator, Horticulture, email@example.com
Pull date: July 30, 2017