Straw is defined as the dried stalks of grain plants, such as wheat, oats, or rye, left over after the grain has been harvested. Straw does not grow grass itself; rather, it functions as a protective covering, or mulch, that supports the successful germination and establishment of applied grass seed.
Defining the Difference Between Straw and Hay
The confusion between straw and growing grass often begins with its close relative, hay. Hay is the dried, whole flowering body of grasses or legumes, like alfalfa or clover, cultivated primarily as feed for livestock. Because hay is harvested while the plant is still green, it retains high nutritional value and a large quantity of viable seeds. Straw, conversely, is a byproduct of the cereal grain industry, consisting mainly of cellulose-rich, hollow stems. After the grain is threshed and removed, the remaining stalks are baled into straw, which possesses low nutritional content. Using hay instead of straw is detrimental because its numerous seeds germinate into unwanted grasses and weeds that compete aggressively with the intended turf.
The Direct Answer: Does Straw Contain Viable Seeds?
While straw is often described as seed-free, the presence of viable seeds is minimal, not entirely absent. The vast majority of the intended seed (the grain) is gone after separation. However, harvesting equipment is not perfectly efficient, and residual grain kernels or weed seeds that grew alongside the crop can remain within the baled straw. When these seeds are introduced to moist conditions over a newly seeded lawn, they may germinate. These sprouts are typically annual grains (like wheat or oat) that die off naturally after one season. The primary risk of using non-certified straw is the introduction of unwanted perennial weed seeds that could establish a permanent presence in the new turf.
Straw’s Primary Role in Supporting Grass Seed Growth
Straw functions as a temporary, light-diffusing mulch over newly sown grass seed. Its primary role is moisture retention; the thin layer creates a barrier that reduces water evaporation from the soil surface. This consistent moisture is necessary for the grass seed’s successful imbibition and germination. The straw also provides temperature regulation by insulating the ground. This prevents extreme temperature fluctuations that can damage delicate, newly emerging seedlings. The physical presence of the straw is also an effective tool for erosion control and seed stabilization. It shields the seeds from being displaced or washed away by heavy rainfall or strong winds, ensuring they remain in contact with the soil.
Selecting and Applying the Right Straw for Seeding
Selecting the Right Straw
The most effective material for this purpose is certified “weed-free” straw, typically sourced from wheat or oats, as it minimizes the risk of introducing foreign seeds. Rice straw is also acceptable, though it can sometimes mat down more easily. Hay should be strictly avoided due to its high seed count. When selecting bales, look for a light, golden color and a dry, loose consistency.
Proper Application
Proper application involves spreading the straw very thinly over the seeded area, a process often described as “tacking.” The goal is to achieve approximately 50 percent coverage, where the soil is still easily visible through the straw layer. This light application is crucial because a thick layer blocks sunlight and air, which can smother emerging seedlings and inhibit growth. The straw should be broken apart into loose strands before spreading to prevent dense clumps or mats. Once the new grass reaches a height of two to three inches, the straw can be left to decompose naturally or removed lightly.