MSU Extension Floriculture & Greenhouse Crop Production

Chemical weed control by application of preemergent (PRE) and postemergent (POST) herbicides is the most effective and economic method to control weeds in landscape planting beds and in container nursery production systems. If the herbicides are applied correctly, there can be little or even negative environmental impacts. Choosing the right herbicide for the target weed species, following the label instructions for the application rate, proper application timing, and following proper calibration procedures are some of the important factors of herbicide efficacy. Currently, nursery growers rely mainly on the application of PRE herbicides than POST herbicides. This is because there are less options for POST available in the market and there are more chances of phytotoxic injury to the ornamental plants (Figure 1) when the POST herbicides are applied directly over-the-top of these ornamentals. Effective and judicious use of these chemical herbicides can lead to excellent weed control in ornamental crop production without causing damage to the environment.