The question of whether to mow before or after applying a weed and feed (W&F) product is a frequent point of confusion for homeowners. W&F is a combination product featuring a selective herbicide to eliminate broadleaf weeds and a fertilizer to nourish the turfgrass. The proper timing of mowing is a major factor in determining the product’s overall effectiveness, ensuring the herbicide works as intended and the fertilizer provides maximum benefit.
Preparing the Lawn Before Application
Mowing the lawn a few days before applying the product is recommended to maximize the herbicide’s contact with the weeds. Broadleaf weeds absorb the chemicals through their foliage, so a longer leaf surface area is desirable for absorption. Mowing too close to the application time, such as within 24 hours, removes the weed’s leaf tissue, the primary site of herbicide entry.
The ideal window is to mow approximately two to four days prior to application. This timeframe allows the grass and weeds to recover from cutting, but it still leaves enough foliage exposed for the herbicide to adhere and penetrate. Cutting the grass slightly lower than normal can also help expose low-growing weeds, such as clover and plantain.
Mowing ahead of time also helps the fertilizer component, particularly with granular products. Shorter grass blades allow the fertilizer granules to settle more easily onto the soil surface, where they are activated by moisture and taken up by the grass roots. This even distribution helps prevent the fertilizer from concentrating in thicker patches, which can lead to localized burning or uneven feeding.
The Critical Wait Time After Application
The answer to whether you should mow immediately after application is no, as the recommended wait time is essential for product success. Mowing too soon significantly reduces the efficacy of both the herbicide and the fertilizer components.
The primary reason for waiting is to allow the herbicide to translocate throughout the weed’s vascular system to kill the entire plant, including the roots. If you mow within 48 to 72 hours of application, the mower blades may clip off the treated foliage before the chemical has fully absorbed. This wastes the product and only trims the weed, allowing it to regrow.
Immediate mowing also negatively impacts the fertilizer component. Most weed and feed products are granular, designed to sit on the soil until dissolved by water. Mowing too quickly can physically displace the granules or suck them up into the mower bag, leading to uneven distribution and product loss. Allowing a waiting period of at least two to three days before mowing ensures the product has time to settle and begin working.
Why Proper Watering is Essential
The effectiveness of weed and feed is dependent on moisture, but the timing of watering is distinct for granular and liquid products.
Granular Products
Granular weed and feed works best when applied to a lawn damp from dew or a light sprinkling. This initial moisture helps the granules stick to the broadleaf weed surfaces, ensuring the herbicide is in direct contact with the foliage for absorption. After the product has been applied, a light watering is necessary, but it must be timed correctly to avoid washing the herbicide off the weeds. For granular products, wait 12 to 24 hours before watering to activate the fertilizer component and help it move into the soil. This delayed watering provides a balance between allowing the herbicide to absorb and activating the fertilizer.
Liquid Products
Liquid weed and feed products are applied to dry grass, and watering must be delayed longer to prevent dilution. It is recommended to wait 24 to 48 hours after application before watering. This gives the chemical time to dry and be fully absorbed by the weed leaves. Watering too soon will wash the liquid herbicide off the foliage, rendering the treatment ineffective.