Some growth regulation is beneficial to most cultivars, but is essential for those cultivars that grow too tall for a quality product. This will reduce final plant height, intensify dark green color of the foliage, and result in a more rounded, uniform product. The most commonly used growth regulator for garden mums is B-Nine. It is applied as a foliar spray at 2500 ppm about 2 weeks after the last pinch. Additional application at the same rate can used if plants begin to stretch, but should not be applied after flower buds are visible.
Late application can reduce flower size.
See Table 3 for a typical growth regulator schedule. They are facultative short-day plants which means that they will eventually flower under any day length but flower much faster when the day length is shorter than the night length. The critical day length for the majority of garden mum cultivars is between 13.5 and 14.5 hours. This means that some cultivars initiate flowers earlier in the season while others initiate flowers later. Garden mum cultivars can be classified by response groups.