Hay as Mulch

“Hay” can make great winter mulch—but you must know just what you’re getting. Here’s the lowdown on straw, hay and salt hay.

Hay is an assortment of forage grasses. It usually includes seeds of grasses and broadleaf weeds, so it is better suited for feeding livestock than for mulching plants.

Straw is a collection of the stems of field crops such as wheat and oats. It is popular as a mulch because it rarely contains weed seeds and is readily available. It makes a particularly good winter mulch because the hollow stems hold air and act as insulation for the plants below.

Salt hay, or salt marsh hay, consists of grasses harvested from salt marshes. Their wiry stems do not mat down or rot as quickly as straw, and any seeds that are present will not germinate because they require wet, saline soil. Where it is available, salt hay is the best choice for mulching.

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10 thoughts on “Hay as Mulch

  1. I used to be a fan of mulching with salt marsh hay; it does work beautifully, lasts all season and no seed germination. However, I was recently made aware of the fact that the harvesting of salt marsh hay is detrimental to the fragile salt marsh ecosystem. Much like using peat moss, this use of a product from another area is counter productive to the global sustainability that many of us would like to achieve in our lives as a whole and in our gardeneing in particular. A better choice is straw; there is at least one brand on the market that has been heat treated to eliminate seed germination. Or, you can solarize any type of locally available straw or hay by wetting it thouroughly and covering it with clear polyethylene to ‘cook’ the seeds. This might take one season and you could use it the next year, simply by planting into it.

  2. I have used hay mulch for my vegetable garden for years and it has suppressed weeds and enriched the soil. Spoiled horse hay is readily available from horse keepers who need to get rid of it. Spoiled hay is hay not suitable to feed to horses. It is dusty and moldy usually from being bailed when not adequately dry, but great for the garden. Hay that includes legumes like alfalfa adds great nutrient rich organic matter to the soil.

  3. If you are planting lots of bulbs ( We did 11,000 for our community gardens) I urge you to dig the entire area up ,then place your bulbs and cover them .I feel this is the easiest way to plant large numbers of bulbs.

  4. I use spoiled horse hay all the time for my vegetable garden and some ‘far away’ perennial beds. Sometimes I let the bales sit out in the rainy weather before I open them. Then I just lay the 2-3 inch “flakes” on the bare soil like a mosaic. I don’t fluff it up. Sometimes I even dump a wheel barrel of FRESH horse poop first! In the spring, I just push it all aside for a planting hole. There are always, everywhere and anywhere, going to be weeds if a seed hits the soil!

    • I have grass hay that was ruined from the Ash from the 1980 eruption of Mt. Saint Helens, in Washington State . Does the seeds of the grass and weeds remain a threat for garden mulch after this 30 year interval of baled storage?

  5. As a horse owner, and user of horse manure in the South, I can say that seeds often pass throw a horse’s digestive tract intact and germinate in the winter (barley and oats) or in the spring (bermudagrass, various weed seeds). While straw and hay from horses is often meticulostly clean, obtaining spent bedding straw from grazed horses can cause major weed problems if you don’t keep the straw layer deep.

  6. Early in my gardening life, I made the big mistake of gathering up soiled hay from a festival’s petting zoo after they left. I thought that since it also had manure mixed in that it would be a great mulch. I didn’t figure on all the farm weed seeds that sprouted the next season.

  7. I am a horticulture Extension agent in SC. We have a large horse industry here which demands extremely high quality hay. Our hay farmers employ very clean practices with weed seed control being a major component. I have successfully used horse-feed grade hay for mulch for years. It breaks down quickly and adds needed organic matter to the soil.

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