Response of Six Begonia Species to Fertilizer Concentration and Substrate pH

Begonia albopicta, B. cucullata var. cucullata, B. echinosepala var. elongatifolia, B. holtonis, B. foliosa var. miniata and B. 'Fuchsifoliosa' are conserved at the Ornamental Plant Germplasm Center (OPGC), in Columbus Ohio as a source of germplasm for breeders and researchers. No cultural information for these species is available. Our objective was to evaluate the response of the above mentioned species to different fertilizer concentrations and substrate pH levels. Rooted cuttings were transplanted into plastic containers using a soilless mix. One of five concentrations ranging from 20 to 600 mg·L -1 N of 17-5-17 water soluble fertilizer were applied in irrigation water for 12 weeks. We found significant responses to the fertilizer concentrations and differences among species on weekly measured substrate EC, shoot length, leaf area, dry weight, average number of inflorescences, and SPAD readings. Growth parameters and visual observations were used to determine optimal fertilizer concentration. High quality B. albopicta, B. cucullata var. cucullata, B. echinosepala var. elongatifolia, and B. holtonis plants were obtained with 200 to 300 mg·L -1 N. On the other hand, low fertilizer concentration was found to be better for B. foliosa var. miniata and B. 'Fuchsifoliosa' in order to avoid high salt stress causing plant death. Seven different pH ranges of the peat-based substrates were obtained by adding different rate of dolomitic hydrated lime ranging from 1.0 to 2.6 kg·m 3 . pH was monitored weekly and maintained accordingly by adding flowable lime or a diluted sulfuric acid solution. The inflorescence number and SPAD readings were significantly different among six species, but there was no significant effect of substrate pH. Significant interaction between species and substrate pH was found in shoot length, leaf area, and dry weight. Substrate pH between 5.6 and 6.0 was found to be adequate for B. albopicta, B. echinosepala var. elongatifolia and B. holtonis. B. foliosa var. miniata plant mortality was observed when grown at a substrate pH below 5.2. The information presented in this work will be useful to OPGC personnel in the maintenance of these species at their facilities, as well as to begonia breeders and collectors.