2014 ASHS Annual Conference

Plant growth regulators (PGR) are used to control plant growth in potted crops to improve compactness for shipping and display. Eucomis L’Herit, a new introduction to the potted crop market, can be unmanageably large in a pot making the use of PGRs desirable. Bulbs of Eucomis ‘Leia’ were grown in the greenhouse and drenched at emergence with one of three plant growth regulators at one of five different rates: 1) flurprimidol (Topflor; 0.25, 0.5, 1, 2, and 4 mg active ingredient per 16.5 cm pot), 2) uniconazole (Sumagic; 0.25, 0.5, 1, 2, and 4 mg a.i.), or 3) paclobutrazol (Piccolo; 0.5, 1, 2, 4 and 8 mg a.i.). An untreated control was also included. As concentration increased days to anthesis increased and foliage height decreased for each PGR. Piccolo (4 and 8 mg), Sumagic (4 mg), and Topflor (2 and 4 mg) treatments reduced the percent of marketable plants to 0% due to excessive stunting of the flowers and are not recommended at the indicated application rates. Topflor had the greatest control over plant growth among all the PGRs. Recommended rates for each PGR are Piccolo at 0.5 mg, Sumagic at 0.25 mg, and Topflor at 0.5 mg based on percent of marketable and flowering plants, foliage and inflorescence height control, and non-excessive lengthening of days to anthesis. Piccolo at 0.5 mg offered the most benefits by increasing percent of marketable and flowering plants by 28%, doubling inflorescence number, and controlling foliage height by 23% from the control.