Garden Mulch – Straw – Does it have to be Organic to be Safe?

Farmers have been spraying herbicides for a long time.  In spite of that, for years organic gardeners were never really concerned about the straw being so contaminated with chemicals that it would effect our vegetable crops — possibly for years — if you used it as mulch.

Then herbicides that belong to a family of chemicals called pyridine that don’t break down readily came on the scene and things changed.  All of sudden we have to be extremely careful of what manures, composts, and mulches we use.

An Important Note:
Make sure you know the difference in Straw and Hay so you won’t confuse the two.
See my post Hay or Straw – Which to use for Mulch.Be extremely careful with hay that is not organic.  It is much more likely to have the long lasting chemicals of the pyridine family on it. (clopyralid, picloram, aninophyralid or aminocyclopyrachlor)You may want to review my post Compost – Mulch – Residual Herbicides – What you can do About Them in Your Garden

We will not belabor at this time all the bad things chemicals do to our soil and gardens but will concentrate on whether or not we  — as organic gardeners — can safely use straw that has been sprayed with herbicides.

The Answer is – it depends on

  • what herbicide/pesticide was sprayed and
  • how long ago.

I have been buying large rolls of straw from the same farmer for over 30 years.  Many persisting herbicides have come on the scene over the past decade. Thus,  I always ask about what if any changes my farmer has made in spraying his wheat fields.  He always says the same thing — “no change” —- but I ALWAYS ask and take nothing for granted.

(And by the way, just so you’ll know —-  straw is the stalk after the wheat grain is cut.)

Straw that I use for mulch (and thus organic matter) in my garden.

Straw that I use for mulch in my garden. This roll was cut the same year I used it.

Even though I’ve known these folks for many years and think a lot of them, it’s still up to me to do my homework and know what the results will be from what they spray.  They’re totally into the chemical way and uninformed enough to think that these chemicals are harmless.

What my Farmer Uses

The wheat that my straw comes from is sprayed with nitrogen and an herbicide called Harmony in January.  In February or March it is sprayed with another herbicide/pesticide called 2, 4-D. (They’ve been using 2,4-D on the wheat ever since I’ve been getting straw from them <almost 35 years> and possibly longer.) (2,4-D is short for 2,4-dichlorophenoxy acetic acid)

Before you gasp in dismay — read all the information first.

I’ll tell you some of the bad stuff first. (Don’t worry — there’s better news after this.)

2,4-D was first used about 1940.

  • You’ll recall that 2, 4-D  is one of the chemicals that was in Agent Orange. (2,4-D can be much more harmful when mixed with another herbicide.)
  • It’s also what Monsanto’s genetically modified corn has in it — so that the corn itself will be immune to the 2,4-D spray.  That means even more of 2,4-D in the environment.
  • If 2,4-D drifts on the wind when sprayed — it can harm susceptible plants like beans, cotton, fruit trees, grapes, legumes, ornamental, peas, tomatoes and other vegetables that are miles away.
  • Excessive amounts of 2,4-D in the soil may temporarily inhibit seed germination and all plant growth.
  • There are other warnings that come with 2,4-D  about not feeding treated forage, fodder, soybeans, or hay to livestock. And the company  warns that hay or forage should not even be cut within 30 days of its application.  Also farmers are warned not to graze their cattle on crops that were sprayed for at least 7 days. Some sources say 14 days. (The same warnings are given for the herbicide Harmony.)

In spite of the Dangers of 2,4-D

There are over 1000 products with this pesticide/herbicide sold in the United States.  It is one of top 3 largest selling pesticides in North America.

The active ingredient in Weed B Gone that many homeowners use is  2,4-D. I wonder how many folks spray their dandelions (or maybe their neighbor sprays) in the spring and then wonder why their vegetable seedlings are not doing too well.  (Or maybe why they’re not feeling too well themselves?)

Here’s the information (the better news) that makes it possible for us to use straw sprayed with Harmony and/or 2, 4-D:

How long Pesticides/Herbicides take to break down — is known as their Half-Life.

Pesticides/herbicides break down through microbial and chemical deterioration.

The time it takes them to breakdown is expressed as Pesticide/Herbicide Half-Life.

The half-life listed for each (in various available charts ) is time required to breakdown under ideal conditions. Persistence of herbicides and pesticides will vary according to different factors including light, temperature, soil moisture, type, ph, etc.

There are 3 categories of Pesticide/Herbicide Half-Life:

  • Nonpersistent – half-life of less than 30 days.
  • Moderate – half-life of 30 to 100 days
  • Persistent (like those in the pyridine family of chemicals) – half life of more than 100 days.

2,4-D Half-Life

Some sources indicate that 2,4-D has a half-life of 7 to 14 days.  I’m no scientist but I figure since there are warnings to the farmers on the instructions that hay or forage should not be cut until at least 30 days after application  — 30 days (or even a bit more to be on the safe side) would be a more accurate half-life.


The half-life I found listed for Harmony was 12 days.

Figuring Safety using my Straw as an Example

Since the wheat crop that my straw comes from was sprayed in January and February, the 2,4-D and Harmony (using the Half-Life of 30 days) have already broken down by the time the straw is cut is cut in early summer.

GardenDmpls, a reader who seems to understand all this better than I do – left a comment to this post that was worth moving into the post. Here’s what she said:

“If they say half life is 7-14 days,but don’t touch until thirty days, that doesn’t mean the half life is around thirty days. Half life is the time it takes for half to break down. If the half life is 7 days, for example, if the original amount was 10 ounces, after one week there would be 5 ounces, a week later 2.5 ounces, after a third week, 1.25 ounces and a fourth week .625 ounces. What is important is when the amount left will be so negligible that you can ignore it.”

Usually by the time I use my straw it’s a year old — sometimes more. But I have used rolls that have just been cut and have never had a problem.  And as I said — I’ve been using the straw for almost 35 years.  (Back then — I knew nothing of residual herbicides.)


These 3 large rolls of straw are more than a year old.

Closing Thoughts

In spite of the fact that man seems to be doing everything he can to destroy the earth, he’s not quite there yet.  Nature is powerful and does lots to help us in our quest to obtain the very best things for our garden so that it can in turn help us be as healthy as possible.

True, it’s not as easy as it use to be.  We can take nothing for granted.  We have to do our homework and search out what is safe and what is not. We must ask questions, get answers, and then know the facts.

If the straw you find has been sprayed with something other than the two chemicals mentioned here, I’ll give you a few sources at the end of this post to make it easier to start your research.

Bottom Line:

If your straw like mine — has been sprayed with Harmony and/or 2,4-D — I feel you can use it safely in your organic garden after the right amount of time has passed and nature has broken down the chemicals.

Certain beds have needed more straw but I didn't want to add it until after a rain. Now is the perfect time!

I’ve loaded my wheelbarrow and am ready to take this load to the garden.

Other Related Posts:

Compost, Mulch, Residual Herbicides – What you Can do About Them in Your Garden

Residual Herbicides in Composts – Part 1

Hay or Straw – Which to use for Mulch

Municipal Compost – Manures – Should You Use Them

A Few Starting Points for Research: This is a good one. Easy to understand and it gives some good tables with information. Gives a chart of half life for various herbicides.
Check this one out. Another good starting point. Very general.
Specimen label directions etc. of 2,4-D weed killer.


Organic Gardening is easy, effective, efficient — and it’s a lot healthier.


All content including photos is copyright by  All Rights Reserved.


  • It’s like having to take chemistry, such a shame that we have to stay ahead like this. But totally necessary. I would swear that a bad bale of straw I bought last year, killed off several batches of my seedlings. It was bought from the local farm store, and I never thought to ask about what was sprayed on it. I’ll bet they had no idea anyway.
    After that graphic demonstration in my garden, I only buy from an organic farm now. But I really never thought about it much until my precious baby seedlings bit the dust.
    What are your plans if your source ever becomes unusable, Theresa? It would be hard to find such an amount of matter to replace it, and it would change your gardening practices tremendously.

  • I thought of that seriously two years ago, Sandra. I’ve been walking in the direction of solving that problem since then.
    I addressed it in a post in January of this year.

    “After more than 30 years of buying my straw from the same family of farmers, I’ve seen the danger of having become dependent on them.  I can’t garden without mulch and lots of it.

    With all that is taking place with residual herbicides, the continued and increased use of chemicals, the increase in GMO crops and the total unawareness of many farmers (including the ones I buy from)  —- I could easily experience a major disaster if I were unable to obtain decent straw for mulch.

    The answer of course would be to grow enough of my own organic material (biomass) that I could eventually work out of being dependent on the farmers for straw. Cover crops like oats and winter rye can do this for me.

    Like anything that is fairly new it’s taking some planning and time to work out the problems that might arise to block the way of my growing exactly as much as I want to as quickly as I want to. It’s not possible at this point for me to reach that goal in one year or even several, but I’m taking steps in that direction.”

  • This is the subject that I needed. I’m having a hard time finding organic wheat straw in GA. Searching all the time. I don`t know where to get organic straw. I’m wondering how I can find out if wheat straw in Lowe`s has been treated with chemicals.

  • Alyona, In addition to looking for straw — see if you can find pine tags that are free for the raking. They are excellent mulch. They will not change the ph of your soil in spite of what you read online.

    Also – be thinking of some cover crops that will give you a lot of biomass. Even if you only plant a small space with something like sudan grass or winter rye — it will help tremendously.

    I’ve just put up a post on how to test for herbicides.

    I doubt that anyone at Lowe’s is going to know about the straw. I wouldn’t trust buying it there anyway. You never know what kind of “bug spray” the people at Lowe’s sprayed on it after it got there. Hard to tell.

    A farm supply place or ideally a farmer is your best source.

  • Thank you Theresa. I grow oat, fava beans and triticale. Also I ordered some buckwheat. I guess I can use a little of cover crops as mulch. I asked my mother-in-law to search for wheat straw in NC. I`ll read the new post to learn more, thank you.

  • If they say half life is 7-14 days,but don’t touch until thirty days, that doesn’t mean the half life is around thirty days. Half life is the time it takes for half to break down. If the half life is 7 days, for example, if the original amount was 10 ounces, after one week there would be 5 ounces, a week later 2.5 ounces, after a third week, 1.25 ounces and a fourth week .625 ounces. What is important is when the amount left will be so negligible that you can ignore it.

  • Triticale sounds interesting, Alyona! Do you grow it for the grain— or just as a cover crop? I guess I’m behind on things, but this is the first I’m hearing about a cross of wheat and rye. I googled it and found that it was first bred in laboratories during the late 19th century in Scotland and Sweden. I found it interesting that it combines the yield potential and grain quality of wheat and the disease tolerance of rye.

    Fava beans are excellent biomass and you probably harvest the beans as well?

    Keep in mind that crops like Sudan grass and winter wheat make lots of biomass that you could use for mulch. You might get 2 to 3 cuttings off the winter wheat for mulch. With Sudan grass you really get a lot of biomass for mulch. You can just keep cutting it.

    And of course, your soil still gets great benefits from the cover crop when you use it as mulch.

    Keep me posted on what you find. You know I’m interested and want you to do well.

  • Thanks for the input GardenDmpls. The sources I gave at the end do not explain it that way. At least I did not understand it to mean that. If you have a better source — please post it when you can.

    I would not know how this information translates. For example: when you say 5 oz. I guess you mean 5 oz of 2, 4-D?
    I would have no way of knowing how many ounces of the chemical had been sprayed. Even if I did — I wouldn’t have the facts to figure how many ounces to a roll of straw.

    What I do know from my own experience — I’ve used rolls of straw in the past that have been sprayed with Harmony and 2,4-D four to five months prior to use and all was well.

  • You can pick up any high school chemistry book and read about the half life of chemicals. GardenDmpls is correct. There is not one source to reference, as it is a basic science principle. You can probably google it. Homeschool resources would be good too. The chemical is not as innocuous as you think. Remember it has been banned in Europe, and the maker of Round-Up found guilty of fraud in France. Be careful of whom you trust. Best wishes!

  • I agree with you 100%. Unfortunately, even though I would much prefer organic straw and although there are many things that I cannot and will not compromise, this is the one thing I have to compromise in order to have my garden. I’m working towards getting away from it, as I hope others are as well.
    Thanks for taking time to comment.

  • Two more things I thought to say after I put up the other reply:

    1. – I never thought the chemical was innocuous (not harmful). By the time the straw goes in my garden, I feel it’s relatively safe although I would still prefer organic if I could get it.
    2. – Regarding – be careful who you trust – readers may want to review prior posts:


  • I have noticed a lot of people struggling to find organic wheat straw. We have a certified organic farm and will be harvesting certified organic wheat straw as well as organically-grown (but not certified as the fields are in transition) beginning in June in large quantities. Our farms are located just over the North Carolina line on the VA side, but we can ship it if it makes sense, and of course provide proof of the certification etc. My email is

  • Thanks for posting your information Timmy. I hope folks will see it and take advantage of what you offer.
    As you said — it’s a struggle to fine organic wheat straw.
    Thanks again.

  • I just bought a truckload of hay to use as mulch in my garden from the same guy I’ve been buying from for a couple of years. For the first time, I asked him what, if anything, he sprays on his hay to eliminate weeds. I was shocked and dismayed when he said 2-4-D. Since I am an organic gardener, that seemed like real bad news. So, I came home and immediately began to research 2-4-D residues on hay. Although I would certainly prefer to be using organically grown hay, I must say, your article has greatly relieved me. I was told the hay had been sprayed at least six weeks before harvest. I will go ahead and use this hay, as I am needing to do some mulching immediately, and I won’t feel too bad about using it. I will, however, begin to search for an organic source. I also had concerns about the manure I have been using, and will investigate that further. I thank you for your information. It has given me some peace of mind.

  • Darrel, I think many of us share your feelings and would much prefer to be using organically grown hay.
    I just hope the situation doesn’t get any worse than it is. At least the stuff they’re using now (2-4D) breaks down after a while.
    I’m glad I could help you and hope you’ll be able to find an organic source.

  • I’ve just read several studies in which decomposing wheat straw inhibited the growth of a corn crop following. .. the application was wheat stubble field being planted to corn on commercial scale, and how this common rotation might be differently organized. It was news to me, has anyone else heard of it?

  • Just started organic gardening I brought some straw for mulching around vegetable is it safe!
    Is there anywhere to test the residual amount of pesticides?
    I purchased it last year in November?
    New Gardener trying to keep pesticides out

  • Paul, I don’t know if your straw if safe or not.
    In this post
    under the heading A simple Test for Manure or Compost — is an example you might possible use by putting straw on top of the soil in the pot (Cut it up so you can make it thick) and watering through the straw.
    Then see if you have any indication of residual pesticides.
    This might not be 100% — but it’s a start.

    If you could find out what the farmer sprayed you’d know for sure. If it’s a long term pesticide then
    you won’t want to use. Otherwise, you’re probably ok.

    In addition it would be beneficial to read this post as well as those recommended at the end of the post.

    Hope this helps. There’s a lot of information on my site that I think will be of benefit. Let me know if you
    have more questions.

    And congratulations on starting with organic!

  • Hi Theresa – What an informative website – thank you. As a brand new gardener, I tried to find organic straw for my raised bed, lettuce & strawberries. It’s getting very hot here in California/Pasadena area. I purchased some straw online; they state “This straw was not sprayed with any chemicals while it was growing or since it has been baled”.
    When I emailed to ask “Is that correct and do you know which chemicals were used on it?”, they replied “Yes that is correct. There was nitrogen fertilizer that was applied before planting and also at planting.”
    My question for you – can a nitrogen fertilizer be as harmful or persistent as Roundup or other herbicides? thanks so much

  • Holly, I don’t know the scientific answer to your question.

    Obviously, nitrogen fertilizer is not an herbicide — so it will not harm crops — at least not in a manner that persistent herbicides would.

    By the time you get the straw the nitrogen fertilizer is more than likely long gone.

    Hope this helps.


  • Hi Theresa. You have been buying wheat straw from the same place for about 35 years. How do you prevent it from turning your garden into a wheat field if none can be guaranteed seed free? The last two bales I bought locally and placed under a tarp are growing. Arghhhhh!

  • Mary, this is such a good question.

    Just for the benefit of other readers — I believe you are referencing a statement I made when we were emailing back and forth about bales of straw you had recently purchased. The bales had been supposedly “guaranteed seed free”. But after you spread the straw, wheat sprouted all over your garden area.

    I have forgotten my exact reply but in essence it was: “No bales of straw can be guaranteed seed free.”

    I should have added more to that statement to further clarify. Thus, the following:

    Specifically when purchasing seed from any place (be it a big box store, farm supply store, or private source) that is not the original source of the straw bales, there is no way for them to claim the straw to be seed free that I know of. Maybe there would be a chemical way — but you and I would not be at all interested in that option (if it exists).

    So, my question to them would be — “How do you know that for a fact?
    In other words – “how can you “guarantee” that straw to be seed free?” And furthermore – “What will you do if it’s not seed free and wheat sprouts all over my garden?”

    Anyone who’s been around as long as you and I have are going to know that last question is futile. I would go so far as to say “nothing” would be the answer to that 100% of the time. It would indeed be most unusual to have them do anything.

    The very best we can do is to buy from a source we know and trust. That can be a hard to do — especially if you’re new to an area and don’t yet know any farmers.

    As of this year I’ve purchased wheat straw from the same family for 42 years. As I mentioned in the post (

    They know what they’re doing when it comes to proper harvesting, but in spite of that I’ve had seed sprout in the garden at least 2 times over 40 years.” (now 42 years)

    I don’t recall the exact problem they were having but whatever it was was beyond their control.

    Here are some reasons I stated in the above mentioned post I linked to:

    “Seed of grain in bales of straw can be a result of it not being harvested properly. Or perhaps the grain head on the harvest machine was not set right.

    “Another reason can be the use of older combines that leave grain in the field that are then picked up by the baler (machine) collecting the straw.

    “There are probably other reasons that are beyond the farmer’s control.” But I don’t know them.

    Anyway – the bottom line and short answer to your question is — 42 years with only 2 years of bales containing seed is about 95% seed free over 4+decades.

    Although I’d prefer a full 42 years without that happening — life has its hurdles. But I’m lucky to have a good source that allows me to be relatively sure I won’t have to go through that scenario again of wheat sprouting all over.

    Hope this better clarifies my initial reply.

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