Troubles associated with growth regulator sprays in Viola wittrockiana plants.
B-Nine, the formulation of daminozide marketed for ornamental crops (Uniroyal Chemicals, Middlebury,
CT), has been used for growth retardation for more than 25 years. Recently, new growth retardants have been
developed, although the response has not been clear for species such as Viola wittrockiana. The troubles have been
associated to excessive stunting, a longer production cycle, and a decrease in plant quality. Our objective was to
evaluate the effect of media quality on the response of Viola wittrockiana plants sprayed with two growth regulators
(Daminozide and Paclobutrazol) at the beginning of the growth cycle. Viola wittrockiana Banner Orange plants were
used. At 25 days from sowing, plants were sprayed with (1) Water (Control), (2) Paclobutrazol: 0.5 mg L-1, (3)
Paclobutrazol: 1.0 mg L-1, (4) Paclobutrazol: 2.5 mg L-1, (5) Paclobutrazol: 5.0 mg L-1, (6) Daminozide: 2,500 mg L-
1. Plugs were planted at 800 cm3 pots (35 days from sowing) in: (1) Fafard Growing Mix®, (2) Fafard Growing Mix®
(50%) + Soil (50%), (3) Soil (100%), (4) Fafard Growing Mix® + River waste (50%), (5) River waste (100%). Our
results showed that the response for a given plant media could change based on the paclobutrazol concentration for
Viola wittrockinana plants and the changes in photoshynthate accumulation could be related to paclobutrazol dosage
and media.