“Weed and Feed” products combine granular fertilizer with a broadleaf herbicide, offering a dual approach to lawn care in a single application. The fertilizer component promotes turfgrass growth, while the herbicide targets unwanted plants. To ensure this combination product works effectively without damaging the lawn, the timing of application relative to your mowing schedule is important. Applying the product too soon or too late can significantly reduce the herbicide’s effectiveness or cause stress to the grass itself. Understanding the recovery period of the turf and the biological mechanism of the weeds is the basis for proper application timing.
Waiting Period Before Applying Weed and Feed
You should allow a minimum of 24 to 48 hours to pass after mowing the lawn before applying a Weed and Feed product. Mowing creates a temporary wound at the tip of each grass blade. Applying fertilizer and herbicide to freshly cut grass can increase the chance of chemical burn on the exposed tissue. The turfgrass needs this short recovery period to minimize susceptibility to chemical stress.
The waiting time is also necessary to maximize the herbicide’s ability to kill weeds. Most broadleaf weed controls are designed to be absorbed through the weed’s foliage, and mowing removes a significant portion of the leaf surface. By waiting two to three days, the weeds have enough surface area to absorb the chemical, and they are actively growing, a state often referred to as high turgor. A healthy, actively growing weed will more readily absorb the herbicide compared to immediate application.
Waiting Period After Applying Weed and Feed
Once the Weed and Feed has been applied, you must wait a minimum of two to four days before the next mowing. This waiting period is important for the success of the herbicide component. Systemic herbicides, which are common in these products, work by being absorbed into the weed’s leaves and then moving down to the root system.
If the lawn is mowed too quickly, the top sections of the weed leaves, where the majority of the herbicide has been absorbed, are removed. This premature cutting eliminates the treatment before it can reach the root, allowing the weed to recover and regrow. The herbicide needs this window of time to travel through the plant’s vascular system to the roots, which is necessary for a complete kill. Longer wait times, up to 72 hours, are advised to ensure maximum translocation and root destruction.
Environmental Factors Affecting Timing and Results
Beyond the mowing schedule, external environmental factors influence the overall effectiveness of a Weed and Feed application.
Moisture Requirements
Moisture is a primary factor, as many granular products require the weed foliage to be damp or wet at the time of application so the granules stick to the leaves. After application, the granules need to be watered in, either by rain or irrigation. This is necessary to dissolve the fertilizer and wash the herbicide off the grass blades and onto the soil surface or the weed leaves for activation.
Temperature Considerations
Temperature is also a consideration, as most herbicides are designed to work best when weeds are actively growing, which generally occurs in moderate temperatures below 85 degrees Fahrenheit. Applying the product during extreme heat can cause the herbicide to volatilize, making it ineffective and potentially causing damage to the turfgrass. Conversely, applying in temperatures that are too cool may slow the weed’s metabolism, preventing the necessary uptake and translocation of the chemical. Conditions that favor active plant growth, such as adequate soil moisture and moderate temperatures, yield the best herbicide results.