2018 ASHS Annual Conference

Consumer performance is critical to the success of greenhouse businesses. In recent years, greenhouse growers have reduced the amount of fertilizer applied to their spring bedding plant crops. This has resulted in concern about the performance of these plants once the consumer has purchased them. An experiment was designed to determine the effect of fertilizer concentration and plant growth regulator during the production phase on the growth of petunias (Petunia x hybrida) in the consumer environment. Petunia ‘Pretty Grand Red’ plugs were transplanted into 6-pack containers (527 ml volume), grown at four concentrations of constant liquid fertilization (50, 100, 150 or 200 ppm N), and treated with four concentrations of paclobutrazol (0, 1, 2 or 3 ppm) in a 4x4 factorial arrangement. At flowering, the plants were placed into a simulated shipping and retail environment for 10 days. Then, the plants were transplanted into 1 L containers and grown for 5 weeks to observe consumer performance. No fertilizer was supplied in the post-production phases. Growth and flowering measurements were made following the consumer phase. Plant height increased linearly as the fertilizer concentration increased. Plant height increased by 34% as the fertilizer concentration increased from 50 to 200 ppm N. All three paclobutrazol treatments reduced plant height by ~15% compared to the untreated control. The number of flowers was highest in 150 and 200 ppm N treatments and there was 62% increase in flower number as the fertilizer concentration increased from 50 to 200 ppm N. Paclobutrazol application resulted in an 11% decrease in flower number. Shoot fresh weight per unit of plant height was used to assess plant quality. Using this measure, the plants grown with 150 and 200 ppm N displayed the highest quality during the consumer phase. Plant growth regulator had no effect on the shoot fresh weight per unit of plant height. The results of this study suggest that fertilizer and plant growth regulation play an important part in petunia growth during and after greenhouse production. In conclusion, low fertility and paclobutrazol applications during the production phase negatively impacted growth and flowering in the consumer phase.