Myths About Straw And Hay In The Garden

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Robert Pavlis

What is the difference between straw and hay? I am always surprised at all of the misinformation that is spread whenever discussions start about using straw or hay in the garden. Which one has more weeds? Do they improve soil? Are lingering herbicides a problem? Should either be used in the garden?

The answers to these questions are quite simple if you first eliminate the myths and that is what I’m going to do in this post.

Myths About Straw And Hay In The Garden
Myths About Straw And Hay In The Garden, source: Bob Dluzen

What Is Hay?

Hay is the harvested part of one or more plants and can include grasses and legumes. In some cases the crop is cut several times in a season in which case it usually does not include the seeds. The crop can also be allowed to mature before harvesting and then it probably includes seeds from both the crop and weeds.

Since hay is harvested from fresh green plants it is usually more nutritious than straw which is why its main use is feeding animals. Its higher nutritional level also makes it more expensive unless it is spoiled, in which case it might be free.

Microbe Science for Gardeners Book, by Robert Pavlis

Hay is made from green plant material and the actual species in it will match the intended use, the local soil conditions and the local environment. Hay is site specific.

The above picture is actually hay. It tends to look like straw once it is dry.

What Is Straw?

Straw is very useful in the garden but it is really an agricultural waste product. The farmer grows some type of grain which is harvested at maturity. The remaining stem is then cut and baled to make straw. The plants are quite dry by the time the grain is harvested and at this stage of growth the plant has used up most of its nutrients to form the grain (the seeds) resulting in a low nutrient stem.

Myth #1: Straw Is Made From Wheat

Straw can be made from any plant where the top part, usually the seeds, is harvested. Wheat is a common source but it can also be made from barley, rye, rice, and oats. Even pea stems are used to make “pea straw”.

Straw is usually used as animal bedding, but it can be used as feed. It’s called straw because the stems are hollow.

Myth #2: Hay Is Made From Legumes

Many people think that hay is made from alfalfa and clover, both of which are legumes. Others think it is made from grass. The truth is that hay is a harvested green plant and can be made from a wide variety of plants including alfalfa, clover, Bermuda, fescue, Timothy and oats. Some people even make it from green wheat plants.

Which type of hay is best for the garden? Grass hay or pasture hay has 10.3 percent crude protein, which compares to a legume hay like early bloom alfalfa with 17.3 percent. More protein means more nitrogen, which is better for the garden. The best hay for you is the one you can get easily at a low price.

Building Natural Ponds book, by Robert Pavlis

Myth #3: Straw Has More Weed Seeds Than Hay

I see this a lot but it’s usually not true. Some grains like wheat are available in Roundup ready form where the herbicide can be used to keep weeds very low. Even when Roundup is not used, fields are normally weed free before planting and the grains shade out many of the weeds. I think that most of the so-called weeds gardeners report from straw is actually sprouted wheat seed.

Hay on the other hand is not usually sprayed with a herbicide and weeds may even be encouraged. When hay is harvested several times during a season the first couple of cuts are usually free of weed seed because it is early in the season, but the last cut might have more weed seeds. If the hay is made from grasses, it can also include grass seed which gardeners see as weeds.

Both straw and hay can be free of weed seed, or they can have lots of weed seeds depending, on how they were grown. One does not necessarily have fewer weeds than the other.

If you find too many weed seeds when using either one as a mulch, you are not mulching thick enough. With enough mulch, the seeds don’t germinate.

Grass hay field ready to mow showing weeds
Grass hay field ready to mow showing weeds, source: Family Farm

Myth #4: Roundup On Straw Will Contaminate Soil

It is a common practice in colder climates to treat wheat, oats and edible beans with Roundup (glyphosate) about two weeks before harvest, a technique called dry-down or desiccation. This kills the plants, speeds up the drying process and makes the harvest more uniform. The procedure allows for an earlier harvest in cold, wet climates.

The unfounded fear of glyphosate has people concerned about contaminating their soil but that is not going to happen. Glyphosate has a relatively short half-life in soil and becomes deactivated when it comes in contact with soil. For more on this see my post, The Truth About Roundup.

What happens when you plant seeds the day after spraying with Roundup? Watch this and see:

In North America, several major food producers are in the process of eliminating pre-harvest treatment with glyphosate, not for health reasons, but because of public pressure and the fact that treatment affects the quality of the grain.

A comment dealing with straw and hay on Facebook starts with, “So much misinformation and misunderstanding in this thread” and the goes on to say “Roundup causes gluten intolerance”!, No it doesn’t, nor does it cause celiac disease – another common myth.

Straw treated with Roundup does exist, but it poses no concern for the gardener.

Myth #5: Straw Is Always A Good Mulch

I love straw as a mulch in vegetable gardens but it is not always a good choice. The problem is that some straw is contaminated with persistent herbicides.

The first point you need to understand is that not all herbicides are a problem. Roundup is not a problem, but growth regulator (PGR) herbicides are. You have to understand every chemical based on its own properties – you can’t paint them all with one brush.

The problem herbicides are the so-called plant growth regulators (PGR) that belong to the pyridine group of compounds and include clopyralid, aminopyralid, aminocyclopyrachlor and picloram. These persistent herbicides remain on the straw and in the soil for several years and can affect plants grown in soil mulched with such straw.

These herbicides can also affect manure as explained in my post Herbicide Contaminated Compost, Straw and Organic Fertilizer.

PGR herbicides tend to affect broadleaf plants so they might be used on grass hay, but not on other types of hay.

It is incorrect to think that these herbicides will contaminate soil forever! The half-life of aminopyralid is about 35 days, which is short, but it will affect plants at very low concentrations (1 ppb), so it can be a problem for a few years.

YouTube video

Myth #6: Hay Is Free Of Herbicides

Hay is less likely to be sprayed with herbicides but it can be. Hay growers may spray to kill broadleaf weeds, but only if it is grass hay.

Myth #7: Straw Contains No Nutrients

This seems to be a common sentiment, but it’s not true. Any plant material contains some nutrients.

An analysis of straw found 3.1% crude protein, 0.1% P and 1.2% K. The same lab found that alfalfa hay contained 18.4% crude protein, 0.2% P and 1.8% K. Hay is generally more nutritious than straw, but straw is nutritious enough for feeding to animals especially in winter when hay is in short supply.

Myth #8: Straw Bale Gardening Works Great

You can make straw bale gardening work, particularly in longer seasons. It can be a good place to garden if you have no useable ground soil, but in any other situation it has few advantages and several disadvantages. For a full review see Straw Bale Garden vs Traditional In-ground Garden – A Critical Comparison.

Hay Can Combust Spontaneously

There is some truth here but this is rarely an issue for gardeners.

Large hay bale on fire
Large hay bale on fire, source: Robert

Hay that is baled too wet will start decomposing and generate heat for the same reason a compost pile gets hot. If enough heat is created, the hay can spontaneously catch on fire. This is a concern when hay is stacked into larger piles and even the large round bales can get hot enough inside to burn. It is unlikely that one or two small bales, even if stacked, will generate enough heat to combust. Once hay is spread out as a mulch layer it won’t generate much heat.

Straw contains less nitrogen which results in slower decomposition and less generated heat. Large wet straw piles found in a barn can be a problem but the small bales of straw used by gardeners are unlikely to self combust. A bale that measures less than 120 F (50 C) is in no danger. They generally need to get over 160 F (70 C) before they spontaneously combust.

Myth #7: Hay Rides Are Fun

They are fun but rare. They are usually straw rides!

Straw Or Hay – Which Is Better?

Straw is a good choice for mulching the vegetable garden provided it does not contain one of the persistent herbicides. Hay will add more nutrients, but is generally more expensive. If you can get spoiled hay for a good price, grab it – there is probably nothing better for mulch.

If weeds are a problem, stack the mulch higher.

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Robert Pavlis

I have been gardening my whole life and have a science background. Besides writing and speaking about gardening, I own and operate a 6 acre private garden called Aspen Grove Gardens which now has over 3,000 perennials, grasses, shrubs and trees. Yes--I am a plantaholic!

17 thoughts on “Myths About Straw And Hay In The Garden”

  1. Hi Bob (my dream husband),
    I’m wondering where in general are some good (safe) sources to get straw for the vegetable garden? I see it at my garden center & at big box stores, farm supply stores.
    This is my first little vegetable garden this spring/summer* and you’ve helped me have more confidence to give some things a go!
    Thanks, as always!
    Stephanie Waltman
    Louisville, KY

    *(except cherry tomatoes, which I don’t really count as they re-seed, grow & produce here whether I want them to or not!)

  2. Herbicide contamination in hay. Hay can be sprayed with herbicides in the Aminopyralid or picloram classes. These include Grazon and Capstone. These herbicides pass through the digestive systems of grazing animals intact and persist in the environment for a very long time. They are gaining notoriety for destroying gardens when manures/compost made from contaminated manures are used. Hay from treated fields is not supposed to be sold off the farm where it was grown, but there seems to be plenty of the stuff escaping into gardens. I do not know if it is used in grain crops. It is becoming necessary for gardeners to know if the sources of their organic materials have been exposed to these chemicals.

  3. Another great article. My roots go back to the Great Plains where we raised alfalfa and clover (hay) and oats and flax (straw). Yes, hay (like freshly mowed grass) can get extremely hot in piles with excessive moisture. Straw is usually put up in a very dry, moisture free state. Straw was pretty much limited to bedding material, where as now it is commonly added as a filler to animal feed. Almost everyone I have contact with in the urban environment understands very little about the difference between the two terms. If weed is defined as a plant you don’t want, straw is on the top with residual seed (oats, wheat, rye, etc.) after the seed heads have been harvested. Just look at a bale of straw as it starts sprouting green blades of “grass” with spring rains.

    I am glad the subject of glyphosate was introduced in this article. I agree with Robert that a lot of folks are not current with the science and regulatory agencies’ views of this particular herbicide. I think some of the confusion goes back to its initial introduction when we were told it would become totally inert once it hit the soil. At least that is my recollection. However, it has been detected in ground and surface water, so perhaps the totality of degradation is not as complete as initially billed. Whether or not it survives and for how long is a separate issue from whether it poses a health risk. The EPA has been quite clear with the glyphosate interim decision in January 2020: “no risks of concern to human health from current uses of glyphosate.” Everyone should at least read the official publication on glyphosate by the EPA, whether you agree with it or not.

    • “become totally inert once it hit the soil” and “it has been detected in ground and surface water” and “total degradation” are not the same thing.

      I don’t think it was ever claimed that it would total degrade when it hit soil. It does become deactivated which means it binds to soil and is not taken up by plant roots. It is still there and therefore labs can detect it. Lab instruments are also very sensitive and can find just about any chemical anywhere in the environment and so “being there” and being there in “biologically significant amounts” are not the same thing.

  4. Your continued defence of Glyso puzzles me. You say you have a “science background” Not sure what that means but the banning of Glyso by many authorities around the world is obviously not just from public pressure. Public pressure has to be backed by the opinions from respected scientists or it would achieve very little in policy outcomes. You do a great job in debunking a lot of ridiculous claims and beliefs but on this issue you are simply not credible. Thank you for your other postings which I will continue to read with interest.

    • I have a back ground in chemistry and biochemistry. I have been following the science of glyphosate for many years.

      Politicians are just people and they need to get elected. Do you really think they don’t follow public pressure?

      If you took the time to read my post about glyphosate, and look at the links in it, you would know that more than 20 government organizations around the world have now agree it does not cause cancer. Many of them have also agreed it does not pose a health risk. The majority of scientists agree. It is only some strong organic-focused groups and the majority of the public that disagrees.

  5. “If you find too many weed seeds when using either one as a mulch, you are not mulching thick enough. With enough mulch, the seeds don’t germinate.” In my opinion, the most important statement. When folks complain about their fear of “weeds” when using straw, I remind them that it’s probably just the odd wheat, oat, or other grain that has sprouted and they are easy to pull out and toss to the chickens. But I rather like the look of them so I usually leave them. Having grown up on a “ranch”(what Californians call a farm that raises cattle), I learned early about the wonderful garden supplies that came from that agriculture. 🙂 I use tall raised beds (arthritis!) for veggies and to fill them, I’ve thrown in a couple of bales of hay (alfalfa, if I’m feeling extravagant) and then good compost/soil mix to fill to the top. Within a year a shovel down into the lowest layer shows it to be almost impossible to discriminate from the compost/soil combo. …. and until then acts like a sponge to soak up water and hold it. I’m stating this just from observation, not from any measurements. We save all the pulled weeds and garden waste for the same purpose: helping to fill raised beds that are 24+ inches high.

  6. Interesting article as usual Robert. I used to live and work on a board acre farm in Western Australia. Hay and straw where both freely available to me in as big a quantity I wanted so I used both. Weeds were a problem for me in the hay. Even in thick layers, any seeds that were viable in the hay germinated, even those near the surface of the hay. The answer to this was to turn the hay every week or so until any seeds left had germinated and been smothered by turning the hay. However this created extra work. The biggest issue I had with using hay was the build up of Slaters (Pill bugs). Their population exploded and when this happened, they turned their attention to eating an seedlings that I planted. I don’t use hay or Straw anymore for this reason. I have found other mulches that don’t cause this Slater issue.


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