Establishing a new lawn from seed requires a protective covering, or mulch, to ensure success. Newly sown grass seed is vulnerable to environmental factors during the germination phase. Mulch ensures the seeds remain in place and provides optimal conditions to sprout successfully, significantly increasing the likelihood of dense turf establishment.
Why Mulching Grass Seed is Necessary
Mulching provides a temporary, insulated environment that improves grass seed germination. The primary function is to maintain consistent soil moisture by acting as a barrier against evaporation from wind and sun exposure. Since grass seeds must remain continually damp for several weeks to sprout, the mulch reduces the need for constant watering.
The covering also regulates soil temperature, preventing fluctuations that can damage delicate seedlings. A light layer of mulch secures the seeds, protecting them from being washed away by heavy rain or scattered by wind erosion. This barrier also helps deter birds, which view freshly scattered seed as an easy food source.
The Preferred Choice: Benefits of Using Straw
The industry standard for covering newly sown grass seed is wheat, oat, or barley straw. Straw is the dry stalk left over after the grain has been harvested, containing very little of the original grain’s seed heads. This lack of viable seed prevents the introduction of unwanted plants into the new lawn.
The lightweight, hollow nature of straw allows it to be spread in a thin layer without smothering the seed. This application permits up to 50% sunlight penetration, necessary for the emerging grass to begin photosynthesis. Straw also decomposes slowly, remaining effective for the entire germination period without becoming a thick, matted barrier.
The Major Drawback of Using Hay
The fundamental difference between hay and straw is their purpose and composition. Hay consists of dried grasses, legumes, and other herbaceous plants harvested as animal feed, often including the entire plant with its seed heads intact. This material contains viable seeds.
When hay is spread over a lawn, the moisture and warmth intended for the grass seed also create ideal conditions for the hay’s own seeds to germinate. This results in contamination of the new lawn with undesirable weeds and non-turf grasses, leading to a long-term maintenance problem.
Hay is also denser than straw. If applied too thickly, it can create a suffocating layer that blocks sunlight and air, hindering new grass growth and potentially ruining the establishment of the desired turf.
Safe Alternatives for Covering Seed
If straw is unavailable, several safe alternatives can provide the necessary protection without the risk of weed contamination.
- Biodegradable erosion control blankets are effective solutions, often made from straw or coconut fiber, that hold seed in place, especially on slopes. These blankets break down over time, eliminating the need for removal.
- A light, quarter-inch layer of screened compost is an excellent choice, as it retains moisture and adds beneficial organic material and nutrients to the soil.
- Peat moss can be used sparingly, offering great moisture retention, but it can be more expensive and may crust over, hindering seedling emergence.
- Commercial paper-based mulches, which often contain a tackifier to bind the material, are also effective, providing a seed-free covering that slowly dissolves with watering.