Water Quality and Calcium plus Magnesium Fertilization Effects on Container-Grown Gardenia and Japanese Holly

Combinations of calcium carbonate with magnesium oxide were found to be superior to dolomite as calcium and magnesium fertilizers for container production of gardenia (Gardenia jasminoides ‘Radicans’) and Japanese holly (Ilex crenata ‘Convexa’). When growth and quality measurements were analyzed, a number of significant water quality by fertilizer interactions were found for both species. In contrast, when responses to water quality and to different rate combinations of calcium carbonate and magnesium oxide (no dolomite) were analyzed, only the visual grade of gardenias showed a significant water quality by fertilizer interaction. Since calcium and magnesium are common constituents of irrigation waters, it is suggested that commercial container nurseries test different rate combinations of calcium carbonate and magnesium oxide for their own water supply and plant species of importance.