Begin the mum season by reviewing your fertilizer program and teaching new employees to recognize symptoms of Chrysanthemum white rust.
Mums are heavy feeders during the first few weeks. Growers use a variety of ways to fertilize mums. Some growers use 100% water soluble fertilizer through a drip system, some use 100% controlled-release fertilizer and some use a combination of water soluble and controlled-release. Regardless of the program you use, start plants off right and prevent premature buds by using moistened soil when potting up plants, then water-in newly planted cuttings with a fertilizer solution.
Avoid stress to young plants during their first 4 to 5 weeks of growth and especially during the first 10 days of the crop or plants will develop buds prematurely and plants will be short. Keep plants moist, well fertilized and properly spaced.
Also check plant roots regularly to monitor plant health.
To encourage soft growth that branches freely, many growers use 200-300 ppm 20-20-20 or a fertilizer that is at least 60% ammonical nitrogen as a constant feed during the first 2-3 weeks. After that they rotate to 200-250 ppm 20-10-20 constant feed. The 20-10-20 contains less ammonical nitrogen. Once plants start to show color, fertilizer is reduced to 100 ppm constant feed.
If using controlled-release fertilizer, keep in mind that the rate of release is affected by its formulation (rate of release), soil temperature and frequency of irrigation. Most formulations release at temperatures of 70°F or above, therefore during cool temperatures, fertilizer may be slow to release. We often have cool temperatures in June when plants need the most fertilizer. This is the reason liquid feed becomes important, to get plants growing and create vegetative growth.
Garden mums initiate flower buds easily and develop rapidly if plants are stressed in any way. If terminal flower buds are observed when cuttings arrive, plants should still perform satisfactorily. Cuttings with terminal flower buds should be pinched hard (allow 4-5 leaves to remain) when they are turgid (4-5 days after planting). This will force out lower breaks which tend to be more vegetative. If both terminal and lateral buds have developed when cuttings arrive, it may be best not to plant them, as they most likely will not perform satisfactorily.
Chrysanthemums are short-day plants. Both flower initiation and development of the flower buds occur more rapidly under short days than long days. However, temperature has a greater influence than day-length on flowering of garden mums. We can experience very cool nights in June. With several cool nights in a row, garden mums can initiate many buds prematurely which results in early flowering of the plants. If premature budding occurs, buds should be pinched off, and adequate moisture and fertilizer supplied. The plants will almost always continue to grow and develop into a quality fall crop.
Tina Smith, UMass Extension
For more information see:
Under "Fall Crops" see these fact sheets:
Growing Garden Mums for Fall Sales
Chrysanthemum White Rust
Garden Mums: Past Problems and Production Tips
Greenhouse Grower, FloriCast: Physiological Disorder on Garden Mums
