Establishing a new lawn from seed requires more than simply scattering the product. Covering the newly sown area with a protective layer is a long-standing practice that significantly improves the probability of a successful, uniform stand of grass. This layer acts as a temporary shelter, creating an optimal microclimate for the delicate germination process. Proper application involves specific material choices and accurate measurements to ensure the seed is protected without being smothered. This guide provides the practical steps and guidance necessary for effectively covering grass seed.
Understanding the Material: Straw Versus Hay
The material used to cover the seed is a fundamental decision, despite the common confusion between the two terms. Hay, which consists of grasses or legumes like alfalfa cut while still containing seed heads, should be actively avoided as a seed covering. Using hay will introduce a large number of unwanted seeds, which will germinate quickly and compete aggressively with your intended grass, leading to a patchy, weed-filled lawn.
Straw, by contrast, is made from the hollow, dry stalks of cereal grains such as wheat, oat, or barley after the grain and seed heads have been removed. This processing makes straw largely seed-free, eliminating the risk of introducing a new crop of weeds to the lawn. For this application, you must choose clean, dry straw that is free of musty odors or excessive debris.
Determining the Correct Coverage Rate
The single most important rule for covering grass seed is to apply the material in a thin, light layer. The goal is to provide enough protection without blocking sunlight or air circulation, which are both necessary for the young seedlings. Visually, the ideal application rate is achieved when roughly 50% to 75% of the soil remains visible through the straw.
The straw should be scattered lightly, not matted down, across the entire seeded area. If the layer is too thick, it can smother emerging seedlings and create a damp environment that encourages fungal growth. A standard square bale, typically weighing between 40 and 80 pounds, is generally sufficient to lightly cover an area ranging from 500 to 1,000 square feet. The actual coverage depends on the bale density and the desired application thickness. To achieve proper coverage, break the bale apart and shake the straw out lightly by hand, rather than placing clumps directly on the soil.
The Role of Mulch in Successful Germination
Applying a thin layer of straw is effective because it modifies the environment directly around the seed, a process known as mulching. One of the primary benefits is moisture retention, as the straw acts as a physical barrier that slows the evaporation of water from the soil surface. This ensures the seeds have consistent access to the moisture required to trigger germination. Seeds that dry out even briefly during this phase may fail to sprout.
The straw also helps to moderate soil temperature, preventing the extreme fluctuations that can stress or damage delicate seedlings. On hot, sunny days, the layer provides necessary shade, and the insulation helps maintain a more stable, warm temperature for sprouting.
Furthermore, the light covering provides physical protection against environmental disturbances. The scattered stalks protect the seeds from being displaced by heavy rain, strong winds, or water runoff, offering erosion control. It also acts as a deterrent, making the seeds less visible and accessible to birds. By maintaining a stable, protected, and moist environment, the straw maximizes the number of seeds that successfully transition to active growth.
Watering and Post-Application Management
The watering protocol for straw-covered grass seed is highly specific and differs significantly from watering an established lawn. The goal is to keep the top inch of soil consistently moist, which typically requires light, frequent watering sessions throughout the day. Immediately after applying the seed and the straw, the area should be watered thoroughly to settle the straw and initiate the germination process.
During the initial phase, before the seedlings emerge, watering two to four times per day for short durations, usually 5 to 10 minutes, is recommended. This should be enough to dampen the straw and the soil surface without causing puddling or runoff that could wash away the seed. As the seedlings begin to grow, you can gradually reduce the frequency of watering while increasing the duration, encouraging the development of deeper root systems.
Once the new grass has established itself and has been mowed for the first time, the straw does not need to be removed. The organic material will naturally begin to break down, adding organic matter back into the soil. Attempting to rake or remove the straw prematurely risks uprooting the fragile young grass plants. Leaving the straw to decompose saves labor and prevents damage to the newly formed turf.