Partial seed retention line #23(‘PSR23’) cuphea is a hybrid of Cuphea viscosissima × C. lanceolata. It is a new, spring-planted, annual, potential oilseed crop that is highly susceptible to interference by weeds because of its slow growth during spring and early summer. Grass weeds are controlled easily in this broadleaf crop, but broadleaf weeds are an appreciable problem. Consequently, several broadleaf herbicides were screened for tolerance by ‘PSR23’ cuphea. Broadleaf herbicides to which cuphea showed tolerance in a spray cabinet and a greenhouse were tested in a field setting for 2 yr. Field tolerance was considered as absence of negative impact (P > 0.05) both years to any of four measured traits: overall vigor, dry weight, stand density, and time to anthesis. Cuphea showed tolerance in the field to three soil-applied herbicides (ethalfluralin, isoxaflutole, and trifluralin) and one postemergence herbicide (mesotrione). A few combinations of soil-applied and postemergence herbicides did not damage cuphea. These combinations were ethalfluralin followed by (fb) mesotrione, isoxaflutole fb imazethapyr, and isoxaflutole fb mesotrione. Availability of these herbicides for use in cuphea production may facilitate the domestication and acceptance of this new crop.

Nomenclature: ‘PSR23’ cuphea, Cuphea viscosissima Jacq. × C. lanceolata f. silenoides W. T. Aiton.

Additional index words: Capric acid, ethalfluralin, isoxaflutole, imazethapyr, lauric acid, mesotrione, oilseed, PSR23, trifluralin.

Abbreviations: fb, followed by; MCFA, medium chain fatty acid; PA, plant-applied; PPI, preplant incorporated; ‘PSR23’, partial seed retention line #23; SA, soil-applied.