Landscape herbicides for controlling various weed problems come in liquid and granular form. Although each has its advantages and disadvantages, many people prefer to apply herbicides as granular rather than as a liquid spray. Sometimes it makes no difference and is just more a matter of personal choice.
Liquid products can be applied with thorough leaf-coverage, which maximizes the amount of herbicide that can enter the targeted weeds. Granules, by contrast, can transfer the herbicide only into the foliage of the target weeds through the point of physical contact, which can be quite small or even non-existent, if the granule simply falls off the leaf and to the soil surface.
Granules must be applied when moisture is present on leaf surfaces, such as on a dewy morning or after watering. The dampness causes the granules to stick to leaf surfaces, increasing the amount of herbicide acting on the weeds. Even then, the degree of control may not match that of liquid spray applications. Spot treatments are not very practical with granular products, so liquids offer that advantage as well.What, then, do granules have going for them? First, they can be applied with a broadcast spreader for efficient application over a large area. Second, they are generally easier to handle and require no mixing. Third, they are not as susceptible to drift as sprays and can often be applied even when a light wind is occurring. Granular products are often formulated with fertilizer as “weed and feed” products, which is convenient. Liquid herbicides, however, can be tank-mixed with liquid fertilizer as well. All in all, root absorbed or soil active materials can be applied well as granules, but foliar active materials should be applied as a spray. The labels of herbicide products will denote the type of activity the herbicide provides such as soil, root and/or foliar.
The LSU AgCenter and the LSU College of Agriculture