Mums may be short day (long night) flowering plants, but they can still flower under long days, especially during cold nights.
Although flowering takes a bit longer, varieties that are Very Early to Mid natural season timing, as listed in the Fresh All Fall Guide, will initiate flower buds under 14.5 hour day lengths. This means you will need to manipulate day length to prevent premature flower bud initiation in April and May, and some areas, June.
Very Early varieties: Brittany Yellow, Michelle Gold, Electra Amber, Keeley Orange, Aideen Red Fire.
Use night interruption mum lighting during propagation and after transplant in April–June; year-round is ideal. A minimum of 10 foot candles of light is needed from 10 p.m. to 2 a.m. each night.
Be sure that night temperatures remain above 62 °F (ideally 65 °F) to prevent flower bud initiation that can occur from cold nights, even in the longest days of the year.
Propagate in larger cells to allow liners to stay inside with night temperature control longer before transplant. Try a 30-cell tray versus a 100-cell to allow liners to start branching and growth before transplant.
Start your garden mum crop later to allow for later transplant. Transplant and move garden mums outdoors in mid to late June, instead of late May and early June, when night temperatures remain above 62 °F. This results in larger finished plants with less crop time because there is no set back from premature bud set.
If you can't control light or temperature, use Florel applications. Treat plants with Florel plant growth regulator when you are not able to adjust the photoperiod with lighting and/or manage the night temperatures. Be sure to start treatments with Florel before the plants are exposed to flower initiation conditions and before buds can be seen. Sprays at 500 ppm every 10 to 14 days are effective. Florel cannot prevent bud initiation when pressure to flower from short day length and cold night temperatures are too strong.
Mum Grower Success Guide
Selection tips for blackcloth, spring, and the Fresh All Fall natural season programs.
Mum Culture Guide
Get your A-Z guide for growing your favorite garden mum families.
Garden Mums At-A-Glance
Key selection, scheduling, and growing information for all garden mum varieties.
2020 New Introductions
Learn about our newest garden mum varieties for the 2020 season.