P&PDL Picture of the Week for
August 5, 2013

Garden Mum Production Challenges

Roberto G. Lopez, Ph.D., Associate Professor & Floriculture Extension Specialist, Purdue University and
Garrett Owen, Ph.D. Student and Floriculture Technician, Purdue University

Temperature

Early-season garden mums that finish short or too early are usually the result of premature budding that occurs when plants are stressed. More specifically, crop exposure to low night temperatures, short days, drought or nutrient stress can lead to premature budding (Figure 1 and 2).

When grown outdoors, growers rely on natural photoperiod (day length) and to a lesser extent temperature to control the timing of the garden mums as they are considered short-day plants. However, temperature can have a greater influence than photoperiod on floral initiation and early development of garden mums. At cool temperatures, early-season mums flower faster under short days and eventually flower under long days. In contrast, at higher temperatures (>85 ºF), short days are required for flowering.

It is not uncommon for garden mums in northern latitudes to be exposed to cool nights. With several consecutive cool nights (50 ºF), garden mums can initiate buds prematurely which results in early flowering and short plants. Premature budding can also be a result of stress from exposure to very high temperatures in combination with low humidity or excessive rainfall. If premature budding occurs, buds should be pinched off immediately, and adequate moisture and fertilizer supplied. Cool temperatures at the end of the production cycle will cause white flowered cultivars to turn pink.

Greenhouse temperatures of 65 to 70 ºF are recommended for the most rapid flower development of garden mums. Lower temperatures can be used to increase flower number and flower size and have relatively little effect on flower development time.

Spacing

Garden mums should not be tightly spaced in the field or in a greenhouse as the shade avoidance response will result in elongated, non-uniform and poor quality plant (Figure 3). As a rule of thumb, garden mums should be spaced on the following schedule - 6” containers, 3 weeks after transplants with a spacing of 12” x 12”; 8” containers, 4 weeks after transplant with a spacing of 15” x 15”; 10” to 14” containers, 5 weeks after transplant with a spacing of 18” x 18” (Figure 4).

Click image to enlarge

Figure 1. Premature flowering

Figures 1 and 2. Premature flowering of garden mums due to cool night temperatures.  

Figure 3. Poor quality garden mum crop due to improper spacing.  

Figure 4. Garden mum crop that has not been properly spaced.    

Purdue Plant & Pest Diagnostic Lab Purdue Cooperative Extension Service