OFA Bulletin Sept/Oct 2010 : Page 3

September/October 2010 • Numb e r 9 2 3 Figure 1. Petunia packs that were left packed tight for too long, resulting in excessive stretch. Figure 3. Petunias grown at night temperatures of 55°F on the left and 65°F on the right. 20-10-20 (8.1% ammoniacal vs 11.9% nitrate nitrogen) can cause soft, rapid vegetative growth. In contrast, a fertilizer like 15-0-15 (2% ammoniacal vs 13% nitrate nitrogen) will result in more deliberate growth. Limiting phosphorus can also result in more compact plants so selecting a fertilizer that is low in phosphorus can be beneficial. Pinching In many cases we plan a pinch into our crop schedule. This Figure 2. Overuse of hanging basket space, which shades the bench crops too much. Fertilizer There is more to pay attention to on a fertilizer label than N-P-K. The source of nitrogen in a fertilizer can greatly affect the growth of our crops. A fertilizer with a high percentage of ammoniacal nitrogen compared to nitrate nitrogen, like can accomplish two goals: promote a more desirable branched growth habit and reduce plant height. Pinching is a labor-intensive task but can be very effective, sometimes too effective. When pinching plants to control plant height it is best to do so when excessive height is anticipated, not after the plants are already much too tall and leggy. Brian Krug University of New Hampshire 38 Academic Way/Spaulding Hall G54 Durham NH, 03824 bkrug@ceunh.unh.edu www.nhfloriculture.com Buy One Full Conference Registration and Everyone Else Comes for $ www.ofaconferences.org PER PERSON 25 September 28-29, 2010 • St. Louis, Missouri O F A B u l l e t i n 3

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