The arrival of spring signals the start of the lawn care season, leading many homeowners to use “weed and feed” products. This popular approach combines fertilizer and weed control into a single application, saving time and effort. Successfully using this dual-action product depends entirely on precise timing to maximize the benefits of both components. This guide provides specific guidance on when to apply weed and feed in the spring for a healthier, weed-free lawn.
Defining Weed and Feed Products
A weed and feed product is fundamentally a mixture of fertilizer and herbicide, designed to stimulate turf growth while simultaneously managing unwanted plants. The fertilizer component provides macro-nutrients, primarily nitrogen, encouraging the grass to grow thicker and greener as it emerges from dormancy. This rapid growth helps the turf naturally outcompete new weed seedlings.
The herbicide portion dictates the application strategy, as it contains either a pre-emergent or a post-emergent chemical. Pre-emergent herbicides create a protective barrier in the soil to stop weed seeds, such as crabgrass, from sprouting. Post-emergent herbicides eliminate weeds already visible above the soil line, like dandelions and clover. The specific type of herbicide is the most important factor for determining the optimal spring timing.
Determining the Optimal Timing Window
The most accurate way to time a spring application is not by the calendar date, but by monitoring environmental indicators, specifically the soil temperature.
Pre-Emergent Timing
For products containing a pre-emergent herbicide aimed at preventing annual weeds like crabgrass, the application window opens when the soil temperature consistently reaches 50°F. The ideal time to apply is when the soil temperature, measured at a depth of 2 to 4 inches, holds steady between 50°F and 55°F for 48 consecutive hours. This temperature range signals that common weed seeds are preparing to germinate, and the pre-emergent must be in place before the seeds sprout. Applying the product too early means the chemical barrier may break down before the weed seeds are active, wasting the product’s effectiveness. This timing also typically coincides with cool-season grasses, such as fescue or Kentucky bluegrass, actively breaking dormancy and beginning their spring growth cycle.
Post-Emergent Timing
If the product contains a post-emergent herbicide, the timing shifts to when broadleaf weeds are actively growing and visible. A good natural indicator is the blooming of forsythia bushes or the emergence of dandelions in the lawn. The weeds must have sufficient leaf surface area to absorb the herbicide, making application to actively growing plants much more effective. The air temperature should be mild, generally between 60°F and 75°F, for the weeds to readily take up the chemical.
Essential Steps for Application Success
Once the optimal timing window has been identified, preparation of the lawn is necessary to ensure the product works as intended. It is best to mow the lawn one or two days before application, which helps the granular product contact the soil or the weed leaves directly. The weather forecast should be checked to confirm there will be no heavy rain or strong winds within 24 to 48 hours of application.
Granular weed and feed products containing post-emergent weed control often require application to a damp or dew-covered lawn so the particles stick to the weed foliage. Before starting, the spreader must be calibrated according to the manufacturer’s instructions on the product bag to ensure an even distribution. Using the wrong setting can lead to over-application, which risks damaging the turf with “fertilizer burn,” or under-application, resulting in poor weed control.
A consistent walking pace and pattern are necessary to avoid overlapping or skipping areas of the lawn. A recommended technique is to apply the product at half the recommended rate, first walking in one direction and then applying the second half perpendicular to the first pass in a crisscross pattern. This method minimizes streaks and ensures complete coverage across the entire area. Always wear protective gloves and long pants when handling and spreading granular lawn products to limit skin exposure.
Post-Application Care
The steps immediately following the application are just as important as the timing to activate the product’s dual functions.
Watering Strategy
For a product that includes a post-emergent herbicide, the lawn should not be watered for 24 to 48 hours to allow the weed-killing chemicals time to fully absorb into the weed leaves. Premature watering will wash the granules off the foliage, significantly reducing the efficacy of the weed control. If the product contains a pre-emergent herbicide, it must be watered into the soil within 12 to 24 hours to activate the protective chemical barrier. A thorough watering also dissolves the fertilizer component, moving the nutrients toward the turf roots and preventing the granules from sitting on the grass blades, which can cause burn damage.
Mowing and Safety
Mowing should be avoided for at least 24 to 72 hours after application to give the granules time to work. Children and pets should be kept off the treated area until the product has been completely watered in and the lawn surface has dried. This simple precaution ensures the safety of people and animals and prevents the chemicals from being tracked into the house.