Avoid ammonium nitrate. For maximum yields of geranium cuttings from mother stock plants the nitrogen supply must be right. Nitrogen can be supplied in two forms, ammonium and nitrate, but in this case ammonium nitrogen should be avoided completely. As the amount of ammonium in the feed increases there is a proportional decrease in the number of cuttings each plant produces. The problem is greatest in inert growing media, where an ammonium nitrate ratio of 8:6 can reduce the number of cuttings from 90 to 70/plant over one year. With a peat/sand mix the problem Is less severe, but the effect can still be seen at higher ammonium ratios.
Source: • Colorado State Flower Growers Association Bulletin #429
Keywords: International Roundup Geraniums