Optimizing Temperature and Timing for Successful Garden Mum Production

As growers are in the full swing of fall garden mum production, understanding the complex relationship between temperature, photoperiod, and environmental stressors is essential for producing high-quality, market-ready plants. As summer brings high temperatures throughout most of the U.S., mum growers face challenges in maintaining plant quality and meeting market timelines. Research from Michigan State University Extension highlights how low or high temperatures, especially during the night, can significantly impact mum growth, development, and marketability. Understanding these effects and implementing adaptive strategies can help growers stay on track for fall sales.

Temperature and Photoperiod: A Delicate Balance

Garden mums are short-day plants, meaning they naturally initiate flowering in late July as day lengths begin to shorten. However, temperature plays an equally critical role, especially during the first two weeks of short days, when flower bud initiation is most sensitive. Cool nights (less than about 60°F, depending on the variety) can trigger premature budding, leading to crown buds that flower prematurely, resulting in flowers buried in the canopy and plants that may not meet market standards for height and uniformity.

Heat Stress and Its Impact on Mums

Conversely, high temperatures above 85°F can cause “heat delay,” pushing flowering back by one to three weeks. Uneven flowering, bud deformation, and crown buds, as well as poor branching, reduced growth, and flower color reversion, are also linked to high temperatures during flower initiation and development. These effects are most pronounced during the first two weeks of short days, a critical period for bud initiation. This delay can disrupt planned shipping schedules and reduce the plants’ appeal at retail.

Temperatures between 65–70°F are recommended for the most rapid flower production, although warmer days (but not warmer nights) are usually fine. However, lower temperatures late in production, once flower initiation is complete, can increase flower number and flower size, while having little effect on crop development time. You can read more about the impacts that temperature has on garden mums in this article, “Temperature on Chrysanthemum.”

For additional information on navigating challenges in garden mum production, including ways to alleviate crown budding and alleviate negative heat effects, read the original article from Caitlin Splawski, Roberto Lopez, and Erik Runkle on the Michigan State University Extension website.