Paclobutrazol and Ancymidol Spray Applications Affect Production Responses and Subsequent Landscape Performance of Ornamental Cabbage, Calendula, and Pansy

Abstract

Previous experiments indicated that plant growth regulators applied during greenhouse production can have a negative effect on subsequent landscape performance of pansy (Viola × wittrockiana H. Gams `Crown Yellow'). Three experiments were initiated in September 2003 to determine the affects of paclobutrazol and ancymidol on production and landscape performance of ornamental cabbage (Brassica oleracea L. var. acephala A.P. deCandolle `Dynasty Pink'), calendula (Calendula officinalis L. `Bon Bon Orange'), and pansy. Seeds were germinated in plug trays (1.5 cm3 inverted cone-shaped pockets) in a growth chamber with a 12 h photoperiod at 25/21 °C day/night. Plants were sprayed with paclobutrazol (formaulated as Bonzi) or ancymidol (formulated as Arest) at plug stage (cabbage, pansy, and calendula on 25 Sept., 2 Oct., 11 Nov., respectively), at 14 days after transplant into 0.73 L containers, or at both stages. Paclobutrazol was applied at 0, 5, 10 or 15 mg·L-1 and ancymidol at 0, 2, 4, or 8 mg·L-1. Cabbage (30 Oct.), pansy (6 Nov.), and calendula (4 Dec.) were transplanted to landscape beds to assess residual effects on growth and flowering. Cabbage and calendula, showed minor differences in growth during greenhouse production due to varying rates of either paclobutrazol or ancymidol, but exhibited a greater response to application time. Only minor differences in growth occurred with pansy during greenhouse production due to rate or time of application using ancymidol, but exhibited major differences in response to both rate and time of application using paclobutrazol. Residual effects on growth and flowering during landscape performance phase will be discussed.