Improving bedding plant quality and stress resistance with low phosphorus

Bedding plants are frequently exposed to water stress during the postproduction period, resulting in reduced quality. We demonstrated that alumina-buffered P fertilizer (Al-P) provides adequate but much lower P concentrations than conventionally used in soilless mixes. When impatiens (Impatiens wallerana Hook. f. 'Impulse Orange') and marigold (Tagetes patula L. 'Janie Tangerine') plants were grown with reduced phosphorus using Al-P, P leaching was greatly reduced and plant quality was improved. Diameter of impatiens plants and leaf area of plants of both species were reduced by Al-P. Marigold plants grown with Al-P had more flowers and fewer wilted flowers. Flower wilting was also reduced for impatiens plants grown with Al-P. In marigold plants, roots were confined to a small volume beneath the drip tube in control plants, while roots of Al-P plants were well distributed through the medium. There was no obvious difference in impatiens root distribution. When plants at the marketing stage were exposed to drought, the Al-P plants of both species wilted more slowly than the conventionally fertilized controls. The reduced leaf area in both species and the improved root distribution of marigold may account for the improvement in drought tolerance of the Al-P plants.