Hay vs. straw mulch? It depends on the source

One of the great things about gardening: You learn something every day.

Case in point: There’s not only a difference between hay and straw, but not all hay is the same either.

This observation came from longtime organic gardener Bob Cooperrider of Lincoln. He grows hay and uses it as mulch for his veggies.

“I like to see accurate information in the newsletter,” wrote Cooperrider to Sacramento Digs Gardening. “So I must respond because this comment about the difference between hay and straw is a common misconception. But it is backwards.”

The misconception? It was contained in Tuesday’s blog post and a recommendation on mulch:

“Many gardeners prefer straw (not hay) because its light color reflects intense sun rays instead of absorbing that added heat. (Also, hay contains seeds that can sprout and suck nutrients out of soil; straw has no seed.)”

With plenty of horse people in my family, I grew up with the axiom, “Hay is food, straw is bedding.” That’s how you could tell them apart; hay had nutritional content while straw did not. (That’s also why a bale of hay costs more than a bale of straw.)

I’ve also learned from experience: Hay mulch can produce lots and lots of sprouts.

At least, it does if that hay came from oats, wheat or other grains. By definition, hay is dried plant material – legumes (alfalfa or clover) or grasses (such as grains, etc.) – used as animal feed.

Hay from alfalfa or clover works fine as mulch. So notes Cooperrider, who has decades of experience.

“As a longtime grain and hay farmer, I can tell you that hay is cuttings of green plants just before they flower,” he explained. “Up to six cuttings of alfalfa hay a year are made in the hotter areas of California. There are no seeds in alfalfa or clover hay, only dried green plants. Hay is highly nutritious and high in nitrogen. It is primarily used as horse and goat feed. 

“Conversely, straw is the stems and some seed heads of grain or grass seed left after harvest of the grain or grass mature plants,” he added. “Straw is what comes out of the back of a grain combine harvester after the mature crop has been cut and threshed by the machine. Straw is very low in nutrients. It’s often used for animal bedding to soak up the animal urine and feces. Straw is not a nutritious feed and it may have some residual seeds left from the threshing of the mature plants.”

Cooperrider shared photos of his own veggie garden, mulched with alfalfa hay.

“Notice that the sun bleaches the green dry alfalfa very quickly to a light color very similar to that of wheat or oat straw,” he said. “I've been an organic gardener and farmer for more than 55 years.”

Cooperrider’s point is that most California hay comes from legumes so won’t sprout when used as mulch while the straw originates from grains and could contain some seed. The alfalfa hay also provides more nitrogen than dried straw.

So, hay can be a recommended mulch – as long as it’s alfalfa or clover hay.

Thanks, Bob!