Growth Responses of Seed Geranium and Petunia to N Source and Growing Media1

Pelargonium hortorum (Bailey) ‘Sprinter Scarlet’ and Petunia hybrida (Bailey) ‘Candy Apple’ seedlings were grown in 2 media and watered with 5 nutrient solutions containing varying ratios of NO 3 − :NH 4 + , each resulting in a total NO 3 − plus NH 4 + concentration of 15 meq liter −1 . There were no significant differences in height, fresh and dry weights, or number of vegetative breaks in soil-grown plants due to the N forms. Plant growth in the soilless medium was substantially reduced as the proportion of NH 4 + increased above 50%.