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is straw full of weed seed

A newly seeded lawn needs to be mulched in order to help keep the top 2 inches of the soil moist. If the soil dries out before the grass becomes established, you’ll wind up with a poor lawn. Once the grass is established, water its soil more deeply and less frequently than previously. Barley straw mulch eventually decomposes and blends into the lawn.

Barley straw, which is the hollow stems remaining after grain is harvested from barley plants (Hordeum vulgare), can be used as an organic mulch. Covering newly planted lawn seeds is among its mulch uses. Barley straw that is suitable for lawn mulch and certified to be free of weed seeds is available.

Apply unrotted barley straw at a rate of 50 to 90 pounds per 1,000 square feet of lawn. That square footage requires one or two bales that each measures about 18 by 14 by 36 inches and weighs 50 to 60 pounds. Most lawns need only a light mulch covering; about 25 percent of the soil should be visible through the mulch. Applying more barley straw may be necessary on a lawn planted on a slope that could erode from rainfall.

Applying Barley Straw Mulch

Use barley straw and not something containing barley straw that is labeled “hay.” Hay, which is usually from a plant other than barley, is used for animal fodder and contains more weed seeds than straw. Clean barley straw is widely used as mulch on recently seeded lawns and does not have a reputation for causing weeds to grow in grass.

Barley straw is highly flammable when it is dry. In general, straw mulches are considered less attractive than some other kinds of mulches. Also, straw lowers the nitrogen level in soil as it decomposes and is subject to being blown by wind.

Low quality hay often has a dull color and different plant stems can be seen. (Photo: Bob Dluzen)

In a garden, however, getting the two confused can lead to problems in the future. Hay and straw are often both used as weed control mulch in the garden but the results you get can be quite different.

Composting hay can reduce the number of weed seeds to a minimum but that has to be done the right way in order for the compost to reach a high enough temperature to kill the seeds. I’d be wary of composted hay unless you’re sure of how it was composted.

Hay is a crop that is grown and harvested as a feed crop for cattle, horses and other farm animals. Straw on the other hand is a byproduct of a grain crop; in our area it’s usually usually wheat straw that we see.

Straw on the other hand, is much better for use as a garden mulch. Since wheat and other grain crops are so competitive in a field, they suppress the growth of many weeds. Farmers also will control weeds one way or another to ensure the highest yields they can get of valuable grain. That results in straw with no or very little weed contamination.

Granted, there are exceptions to the rule. You can find weed-free hay, such as 100% alfalfa or timothy but these can be expensive. Sometimes straw can be highly contaminated with weeds if it was grown in less than optimum conditions.

You never know what plant combination you’ll get in a random bale of hay. More often than not they contain weeds that you can inadvertently introduce to your property. I’ve seen such tenacious perennial weeds like thistle come into a garden as a result of their seeds hiding inside a bale of hay.