Q • I transplanted my hardy mums to a new location in my garden last fall. I fertilized them this spring, and they are growing fast and getting tall but are already starting to set buds. I have not cut them back yet. To develop bushy plants, I know I should pinch the growing tips. Could you provide information on the method of pinching and when to pinch and what time to stop pinching?
It’s always best to cut mums back every spring shortly after they first begin to grow. Timing is everything. If you don’t cut mums back in early spring, then they are more likely to produce a premature and disappointing period of poor bloom in summer and a lackluster season of poor bloom in fall.
Now that your mums have gotten too tall, they might be too woody to pinch, so you may have to cut them back first with a pair of hand pruners or sharp hedge shears. Lower the height to about 6-12 inches from the ground, even if it means cutting off the flower buds that have already formed. Then, when they produce 4 to 6 inches of new growth, pinch out just the growing tips.
Pinching is just that — using your thumb and forefinger to nip off the succulent new growth at the very tip of the stem, removing no more than the top two leaves on each. As a result, two stems will grow from below each pinch, so once those put on another 4 to 6 inches of new growth, you’ll have twice as much work to do. However many “pinching sessions” you have to make is determined by how fast the mum grows. Then you want to pinch them one last time close to, but no later than, mid-July. By then the days are already starting to get noticeably shorter, and in response to decreasing daylight, your mums will set flower buds on the tips of all those stocky new stems you’ve encouraged to grow.
If you pinch too late, you may delay their flowering until after their normal blooming time. For some varieties this could cause them to flower so close to frost that it hardly makes it worthwhile to have grown them in the first place.
Write to Chip Tynan at chip.tynan@mobot.org or Horticultural Answer Service, Department PD, P.O. Box 299, St. Louis, Mo. 63166. Check his blog at: mobot.org/gardeninghelp/hilight.asp
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