A light layer of covering material placed over newly sown grass seed is a common practice for establishing a new lawn or repairing bare patches. This technique, though often described using the generic term “hay,” is a deliberate form of mulching used to maximize the success of grass seed germination. The covering creates an optimized microclimate around the seed, providing protection and promoting the biological conditions necessary for successful sprouting. The application is meant to be temporary, yet it plays an important role during the seed’s vulnerable life cycle.
Preventing Erosion and Seed Displacement
The primary mechanical function of the covering is to physically stabilize the seed and the soil surface. Unprotected seeds are vulnerable to displacement from environmental factors like heavy rain or strong wind. A sudden downpour can easily wash tiny seeds into clumps or drainage areas, leading to uneven and patchy turf growth across the lawn.
The loose, fibrous material acts as a physical buffer, absorbing the impact energy of raindrops and preventing the soil from splashing and crusting over the seeds. This barrier also discourages birds and small mammals from feeding on the exposed seeds, which can lead to significant loss of the planted material. By holding the seed in place until the root system develops, the covering ensures a more uniform distribution of the grass stand.
Regulating Moisture and Soil Temperature
Beyond physical protection, the covering material creates a more favorable environment for the germination process. Grass seeds require consistent moisture to break dormancy and sprout, and the thin layer of mulch significantly reduces the rate of water evaporation from the soil surface. This means the soil stays damp for longer periods, decreasing the need for constant, light watering.
The layer also helps to moderate the soil temperature, acting as a form of insulation. It shields the dark soil from intense direct sunlight, preventing it from overheating, while also trapping warmth during cooler periods. Maintaining a stable, optimal temperature range and ensuring continuous hydration are factors that enhance the germination rate and speed of the new grass.
Choosing and Applying the Best Covering Material
The commonly used term “hay” refers to cut grasses and legumes used for animal feed, which frequently contains viable seeds. Using true hay will introduce unwanted weeds or aggressive grasses that compete with the new lawn for nutrients and water.
The recommended material is straw, specifically the dried, hollow stems of cereal grains like wheat, oat, or barley, harvested after the seed heads have been removed. Clean straw is largely seed-free, preventing the introduction of invasive plants. When applying it, the layer must be extremely thin and loose, allowing approximately 50 to 75 percent of the soil to remain visible underneath. Applying the straw too thickly will block sunlight, reduce air circulation, and can physically smother emerging seedlings, negating the material’s benefits.
What Happens After the Grass Sprouts
Once the grass seeds have germinated and the seedlings reach a height of about two to three inches, the temporary covering has served its purpose. Properly applied straw does not require removal as it is biodegradable and will naturally decompose into the soil. This decomposition process returns organic matter to the soil, providing a minor nutrient boost to the young grass.
When the new grass is tall enough for its first mowing, the remaining straw can simply be mowed over with the deck set to its highest setting. At this stage, the watering schedule should transition from light, frequent applications necessary for germination to deeper, less frequent watering to encourage the development of a strong, established root system.