OFA Bulletin September/October 2011 : Page 3

September/October 2011 • Number 929 Dresselhuys explains the needs of the young chrysanthemum. “It needs water, nutrition, and space to grow. Make sure you provide that and have your pest management and disease management in place. Prevention is the key word, because you can’t reach plagues or diseases very well with your chemicals when the plant is well established.” Royal Heins agrees, but wants to warn the growers as well: “Contrary to popular belief, garden chrysanthemums do not require, and will not use nutrients when applied in excess of 125 ppm nitrogen on a constant basis. Higher rates will either need to be leached or will accumulate in the media raising EC. Constant feed (at 100 to 125 ppm nitrogen from a fertilizer such as 17-5-17) at every watering will produce excellent plants without the fertilizer waste typical of higher rates. However, it is important to make sure that plants are getting adequate amounts of micronutrients, which may mean augmenting the fertilizer program. Plants should receive 1 ppm iron, 0.5 ppm manganese, 0.5 ppm zinc, 0.3 ppm copper, 0.25 ppm boron, and 0.1 ppm molybdenum. It is all about nitrogen management but with adequate concentrations of other nutrients.” Flowering induction in garden chrysanthemums is promoted by short days and cool night temperatures. But, Heins explains, “Even under long days, premature bud set can occur if night temperatures fall below 68°F. To ensure plants do not form premature flowers, apply Florel (generally 500 ppm) during the vegetative phase. As a general rule, the first application about 7 to 10 days after sticking will prevent premature flower-bud set in the liner, and application every 2 weeks after transplant up to no closer than 8 weeks to ship will prevent premature flower bud set. It is much easier to use Florel to prevent early bud set than to correct early bud set. By the way, high fertility does not prevent flowering contrary to popular belief.” Flowering You want your crop to finish on time and have the right shape. Give the right number of long days for plant bulking. Natural day length on any day of the year varies with latitude. On any given summer day, day length is longer in the North (e.g. Michigan) than in the South (e.g. Texas). Warmer summer temperatures in southern states normally work to prevent premature flower bud set in June and July even as the natural day length in the south, even in mid-June, is more conducive for flower induction, especially if temperatures turn cool. The longest day length in June in North Carolina is the same as the day length the first of August in mid-Michigan and Connecticut. By the third week of August, black-out should not be needed anywhere in the United States to shorten day length, according to Royal Heins. When growing mums in larger pots, you should consider putting hoops on the pots or putting a net around the plant to prevent it from falling apart. This is especially important for plants grown inside greenhouses where higher temperatures and lower light levels typically lead to weaker plants. Hoops and netting are “shrink insurance,” allowing you to sell more plants because fewer fall apart and need to be dumped. Timing Figure 3. Great-looking garden mums Asked about the do’s and don’ts in chrysanthemum culture, Heins and Dresselhuys are unanimous. Do’s & Don’ts Do’s 1. 2. 3. 4. 5. Choose the right variety for the pot size and climate Propagate properly to start Control the flowering time, prevent premature budding Control the height Have your pest and disease management in place Figure 2. Garden mums with 12-inch spacing. Don’ts It is very important to stay on top of pests and diseases, especially in the early stage of the crop. Dresselhuys states, “It is more difficult for sprays to penetrate the plant during later stages of production, so make sure you keep pests under control, earlier in the vegetative state.” Royal Heins adds more to this. “The chrysanthemum crop is usually attacked by leaf miners, spider mites, aphids, Pythium, and Rhizoctonia. Make sure you have a regular scouting program in place and take action when you see something happening. Of course, prevention is better. I always recommend preventative spray programs for insects and foliage diseases and drenches for soil pathogens.” OF A Bulletin Pest & Disease management 1. Over fertilize 2. Stress the plant in terms of drought, temperature, etc which can cause premature budding 3. Crowd plants – space on time; the plant needs space to develop right Mark Schermer Fides North America 805-525-7125 805-525-3412 m.schermer@fidesno-rthamerica.com 3

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