Why Put Straw on Newly Seeded Lawns?

Benefits of Mulch

• In small patches, grass seed is best mulched with a light layer of peat. Straw pieces substitute better in larger seeded areas, mainly because of cost. Light, airy layers of these mulches placed over freshly planted lawn seed shades the soil and seed. This leads to cooler temperatures and slowed drying by reduced evaporation. Cooler, moist soil leads to better, more widespread seed germination. On hillsides, the cross-hatching fibers of straw reduce erosion of soil after rains or prevents winds from blowing grass seed. In some regions, straw over the soil prevents hungry songbirds from eating seed.

Amount Needed

• Straw mulch atop a newly seeded area needs to be the appropriate thickness and consistency. Sparse straw allows soil to dry out, while too thick of a layer leads to mold or lack of sunlight that kills seedlings. This requires raking and removal of straw -- a tedious step. One bale of clean, weed seed-free straw effectively covers 1,000 square feet of seeded lawn area, according to Purdue University. If sowing seed in fall or on drier, lighter-textured sandy soils, increase the density of straw particles so one bale covers 800 square feet. You always want to see no less than 50 percent soil through the fibers of laid straw mulch.

Aftercare

• Appropriately laid and distributed straw mulch requires no aftercare, even once the lawn seedlings pop up through the layer. As long as the grass plants bask in sunlight and soil remains evenly moist, there's no need to rake up the straw bits. Allow the straw to naturally decompose over a year. Once the new lawn attains an age and density warranting mowing, the cutting blades may upend some straw. Bits chopped up by the mower can fall onto the lawn and decompose. In time, the straw bits work their way downward to the soil surface, to be well covered by the thick carpet of grass blades.

Lawn Grass Types

• Gardeners in the United States use two types of lawn grasses: cool-season and warm-season grasses. Cool-season grasses, such as bluegrass and fescue, most often are grown from seed. Warm-season grasses, such as St. Augustine, zoysiagrass and bermudagrass, are established from plugs or sprigs. Any type of lawn started from cut sod pieces never receives a straw mulch. Straw may be used when small grass sprigs are planted in some regions. Contact your local cooperative extension office for recommendations on the use of straw on lawns planted with sprigs or plugs.