W&F products combine fertilizer and herbicide into a single, dual-action application for lawn care. While convenient, the frequency of application is critical for maintaining a healthy lawn and avoiding unintended consequences. Understanding the strict limits on using these growth stimulants and chemical controls is paramount for turf health and environmental safety. The goal is to provide necessary nutrients and weed control without causing damage through chemical overload.
Understanding the Active Ingredients
W&F products contain two distinct chemical types: fertilizer and herbicide. The fertilizer component typically includes nitrogen, phosphorus, and potassium (N-P-K), macronutrients that stimulate growth and improve color. Nitrogen causes the rapid greening effect, but frequent application can cause problems.
The herbicide component is designed to kill broadleaf weeds, often using compounds like 2,4-D, MCPP, and Dicamba. These are post-emergent chemicals that target weeds that have already sprouted and are actively growing. Overuse of nitrogen fertilizer can cause “fertilizer burn,” where salts draw moisture out of the grass blades, causing them to brown and die.
Applying W&F too often risks accumulating herbicides in the soil, which can harm non-target plants like nearby trees and shrubs. Excessive application also increases the potential for chemical runoff into water systems, posing environmental concerns for aquatic life. This dual risk of lawn damage and environmental contamination is the primary reason for strictly limiting application frequency.
Establishing the Seasonal Application Limits
Industry recommendations limit W&F use to a maximum of two to three applications per growing season to prevent chemical accumulation damage. The standard schedule involves one application in the spring and a second in the early fall, aligning with the periods of most active growth for grass and weeds. This timing ensures that the lawn receives a boost when it needs it most.
The minimum waiting period between applications is strict, usually 6 to 8 weeks (approximately two months). This allows the active herbicide ingredients to degrade, preventing chemical levels in the soil from damaging the turf or environment. Using W&F outside this frequency can lead to weak, forced grass growth, making it susceptible to disease and pests.
This two-to-three-times-per-year limit guides total W&F use. If a fertilizer-only product is applied, it must be factored into the overall seasonal nitrogen load. The spring application typically targets weeds like dandelions as they emerge from dormancy, while the fall treatment helps the lawn recover from summer stress and prepares for winter.
Environmental and Procedural Timing Factors
Beyond the annual limit, the immediate environmental conditions are critical for determining the specific day an application should occur. Granular W&F products require the weed leaves to be moist so the herbicide granules can stick to the surface and be absorbed by the plant. Applying the product when there is dew on the grass, typically in the early morning, optimizes this contact for maximum weed-killing effectiveness.
Temperature is another major factor, as applying W&F during periods of extreme heat can cause the fertilizer salts to burn the grass blades. The ideal air temperature for application is generally between 60°F and 90°F, as this range ensures that both the grass and the weeds are actively growing and able to absorb the chemicals. Avoid treating the lawn during a drought or heatwave, as the lack of moisture increases the risk of turf damage.
Procedural timing related to mowing is also important. It is best to mow the lawn two to four days before application. This gives the weeds time to recover some leaf surface, which is necessary for absorbing the herbicide. Following the application, the lawn should not be mowed for at least one to three days to allow the herbicide sufficient time to be translocated down to the weed’s root system. Finally, heavy rain should be avoided immediately after application, as it can wash away the product before it has a chance to work, leading to wasted product and potential runoff.