Overwatered spring crops are subject to a range of biotic and abiotic disorders including hypoxia, nutrient deficiencies, and increased susceptibility to root rot diseases. Defining parameters associated with under- and overwatering would demonstrate how watering practices influence growth and abiotic disorders that develop during greenhouse production. Growth and nutrient content of petunia ‘Cascadias Indian Summer’ (IS) and ‘Headliner Strawberry Sky’ (SS; Expt. 1) and calibrachoa ‘Aloha Kona Midnight Blue’ (MB; Expt. 2) plants were grown under three different watering regimes of overwatered (rewatered when weight of sentinel pots dropped to 90 to 95 5% of container capacity, CC), optimally watered (60 5% of CC), and underwatered (35 to 45 5% of CC) and two different fertilizer sources of Jack’s Professional General Purpose and Jack’s Classic Petunia Feed. Across both plant species, the optimal watering regime generally yielded the largest plants based on width, fresh and dry weights. SPAD readings of youngest foliage were different based on fertilizer source. While IS petunia did not develop yellowing of youngest foliage in any treatment, SS petunia developed distinctive symptoms of interveinal chlorosis in youngest foliage of overwatered plants fertilized with general purpose fertilizer. However, tissue analysis of SS petunia revealed no difference in Fe between watering regimes or fertilizer formulations. Differences did occur across watering regimes in tissue P, K, Ca, Mg, S, and Mn and between fertilizer formulations in P, Mg, and S. Overwatering induced visual symptomology of chlorotic young foliage in SS petunia and MB calibrachoa, but not IS petunia, which suggests a genetic component to the disorder. Symptomology is effectively mitigated by using petunia feed. Tissue nutrient content is affected by overwatering, but Fe is not significantly different. Future work will explore a mechanism associated with substrate microbial activity that explains these results.
