Spring fertilization is crucial for establishing a dense, deeply colored lawn and helping turf recover from winter dormancy. Proper feeding prepares the grass to withstand the stresses of summer heat and drought. Successful spring feeding relies less on a specific calendar date and more on monitoring soil conditions, selecting the proper product, and executing the application with precision. This guide covers the timing and technique necessary for effective nutrient delivery.
Defining the Optimal Timing
Determining the precise time to apply spring fertilizer depends on the soil temperature, which dictates when the turfgrass begins its active growth cycle. Timing differs based on whether the grass is a cool-season or warm-season variety. Applying fertilizer too early risks feeding weeds and promoting excessive leaf growth before the roots are ready to support it.
Cool-season grasses, such as Kentucky Bluegrass, Fescue, and Perennial Ryegrass, surge when soil temperatures consistently reach 55°F. The first primary fertilizer application should be delayed until late spring or early summer, after the initial rapid growth flush has subsided. Fertilizing too soon forces the grass to prioritize shoot growth over developing deep, resilient root systems necessary for summer survival.
Warm-season grasses, including Bermuda, Zoysia, and St. Augustine, require later timing as they thrive in heat. The first feeding should coincide with the grass fully emerging from dormancy when soil temperatures are consistently between 65°F and 70°F. This later window ensures the grass is actively growing and ready to absorb nitrogen, preventing the nutrients from simply leaching away into the soil.
The main spring fertilization must be differentiated from the application of a pre-emergent herbicide, often applied around the time soil temperatures reach 50°F. The pre-emergent barrier is put down to stop crabgrass seeds from germinating before the turf is actively growing. The main fertilizer application should be timed later to support sustained growth rather than an explosive, short-lived growth spurt.
Pre-Fertilization Checklist
Before spreading fertilizer, several preparatory steps ensure the lawn efficiently absorbs nutrients. The first step involves a thorough cleanup, removing heavy layers of debris, sticks, and matted leaf litter accumulated over the winter. This action ensures the fertilizer granules make direct contact with the soil surface.
The lawn should be mowed to its proper height just before application. Mowing removes excess grass blade length, allowing the fertilizer to fall straight to the soil. Conducting a soil test is beneficial, as it is the only reliable way to identify specific deficiencies in nutrients like phosphorus (P) or potassium (K). A soil test prevents the unnecessary application of nutrients the grass does not need.
If the lawn suffers from severe soil compaction or a thick layer of thatch, core aeration or dethatching should occur before fertilization. Aeration pulls small plugs of soil, creating channels that allow air, water, and nutrients to penetrate deeply into the root zone. Performing this step ensures the newly applied fertilizer reaches the deep roots, maximizing the effectiveness of the spring feeding.
Choosing the Right Spring Fertilizer
When selecting a spring fertilizer, understanding the NPK ratio, represented by three numbers on the bag, is important for healthy growth. These numbers stand for the percentage by weight of Nitrogen (N), Phosphorus (P), and Potassium (K). Since the goal of spring feeding is to promote top growth and deep green color, a fertilizer with a high nitrogen concentration is recommended, often following a ratio like 4:1:2 or 3:1:2.
Nitrogen is the most important component in the spring, driving the lush color and density associated with a healthy lawn. Phosphorus supports root development, and potassium aids in overall plant health, stress resistance, and water regulation. Selecting a ratio that favors nitrogen, such as a 20-5-10 blend, provides the necessary boost without over-applying the other nutrients, especially if a soil test has shown they are already present in sufficient amounts.
The choice between slow-release and quick-release nitrogen formulation significantly impacts the lawn’s growth pattern. Quick-release fertilizers are water-soluble, providing an immediate surge of nutrients that results in a rapid green-up and a sudden, intense growth spurt. Slow-release fertilizers, which are often coated granules, provide a steady, metered supply of nitrogen over six to eight weeks, promoting more uniform growth and reducing the risk of fertilizer burn. For spring, a slow-release option is preferred to avoid the stress of excessive growth and the need for frequent mowing.
It is best to avoid combination products known as “weed and feed” for the main spring fertilizer application. These products contain both fertilizer and a broadleaf weed killer, and their timing requirements often conflict. The ideal time to apply fertilizer for grass health does not align perfectly with the best time to apply a herbicide for effective weed control, making separate, targeted applications a more effective strategy.
Application and Immediate Follow-Up
Applying granular fertilizer requires the use of a mechanical spreader. Fill the spreader on a hard surface like a driveway or sidewalk, never on the lawn itself. This precaution minimizes the risk of concentrated spills that can severely burn the grass. Any granules accidentally spilled onto paved surfaces should be immediately swept up and returned to the spreader or scattered back onto the lawn to prevent them from washing into storm drains.
To ensure completely uniform coverage and avoid visible stripes, the total amount of fertilizer should be divided in half. Apply the first half by walking in parallel rows across the lawn in one direction. Then, apply the second half by walking in parallel rows perpendicular to the first pass. Maintaining a consistent walking speed is important, as the rate of granule dispersal is directly tied to the speed of the spreader.
The most critical step immediately following the application of granular fertilizer is watering the lawn. Granules must be watered in promptly, ideally within a few hours, to activate the nutrients and dissolve the salt content. If the granules are left sitting on the grass blades, they will draw moisture out of the plant tissue, leading to a condition known as fertilizer burn. A light but thorough watering, aiming for about a quarter to a half inch of water, is usually sufficient to move the fertilizer into the soil without causing nutrient runoff.
After the fertilizer has been applied and watered in, a waiting period is necessary before resuming normal lawn activities. Wait at least 24 to 48 hours before mowing the lawn again to ensure the nutrients have been fully absorbed and the blades are dry. Furthermore, keep pets and children off the treated area for at least 24 to 72 hours, or until the lawn is completely dry, to prevent contact with the fertilizer granules.