Weeds are difficult to control in potted tropical ornamentals, especially when plants are kept for extended time periods at a nursery. Management is complicated by the lack of tolerance data for many tropical species. Experiments were conducted in 2015, 2016, and 2017 at the Gulf Coast Research and Education Center in Balm, FL, to evaluate tolerance of stromanthe, croton, philodendron, arbicola, cordyline, ixora, plumbago, allamanda, bird-of-paradise, firebush, and hibiscus to granular applications of indaziflam, flumioxazin, pendimethalin + oxyfluorfen, pendimethalin + dimethenamid-P, trifluralin + oxyfluorfen + isoxaben, and trifluralin + isoxaben, and liquid applications of prodiamine + isoxaben and dimethenamid-P. Indaziflam, pendimethalin + oxyfluorfen, and trifluralin + oxyfluorfen + isoxabin were safe for use on all evaluated ornamentals except stromanthe. Dimethenamid-P and pendimethalin + oxyfluorfen were safe on all evaluated ornamentals except allamanda. Flumioxazin damaged philodendron and bird-of-paradise but was safe on all other ornamentals tested. Trifluralin + isoxaben and prodiamine + isoxaben were safe on hibiscus, firebush, and bird-of-paradise, but prodiamine + isoxaben damaged allamanda. We have identified multiple PRE herbicides that can safely be used on multiple tropical ornamentals grown in containers.

Metolachlor, applied to the surface of leaching columns as dicalcium phosphate tablets, was recovered over a period of 25 d compared with 2 and 3 d for emulsifiable concentrate and granular formulations, respectively. In similar studies, approximately 27% of napropamide was recovered from tablets during the same period. Adding an adjuvant to the napropamide tablet mixture increased the recovery rate to 55%. Tablet hardness and size had little effect on the release rate of napropamide. Tablets containing 4% ai napropamide released greater amounts of herbicide at a single collection period than did tablets containing 1% ai. Adding an adjuvant to the napropamide tablet mixture significantly improved Italian ryegrass control in the area adjacent to herbicide placement.