Healthy Compost with a young toad at Raised Roots Co Kitchen Gardens

Is Your Compost a Killer?

Gardening Tips

Compost is the wonder component of thriving, gorgeous, and wildly productive gardens. Writing about compost in a dangerous light is difficult for me because I am so passionate about compost! It’s also much more cumbersome, and a lot more technical than my norm. I’ve meant to tackle this post for a few years now. Yes, years. Somehow I always managed to put it off. However, I’ve noticed a significant uptick in killer compost cases on social media forums. I became aware of a cluster of cases in the Pacific Northwest recently, and it’s also hitting market farmers. So the time is nigh to write out my thoughts and share them with you.

Killer Compost? Really?

The same compost you know and love could be hiding a deadly and insidious component. It will wreak havoc on your garden not only for this year but possibly for years to come. It will require a significant investment of time and interventions to get it under control. In many cases, it requires the removal of every last bit of garden soil. 

Do I have your attention now? Good. It is one of the most potentially devastating issues we’ll face in our local homegrown food supply. And our kitchen gardens. 

For more than a decade, this compost has destroyed gardens. However, there have only been a few articles written about it, and none truly targets the home gardener.

What is Killer Compost?

Killer Compost comes from composted manure of grazing animals. We have a horse farm with a goat and free-ranging chickens. Composted manures make up the bulk of the nutrients in our fertile, hand-blended soil on the farm. 

Grazing animals rely on pasture grasses and other forage for the bulk of their diet. For people without the ability to keep their animals on pasture, feeding baled forage products such as hay and chopped hay products is a must.

In their efforts to produce the best grazing and hay possible, producers and farmers need to keep broadleaf weeds under control. This will keep timothy or other grasses and grains growing relatively weed-free. It’s not only an economic need but for safety as well. Certain noxious weeds like Buttercup, Alsike Clover, Jimsonweed, Nightshades, and others can be poisonous for horses and other grazing animals. It’s imperative to eliminate them from grazing and forage products. 

Unfortunately, these weeds can be tough to eradicate, really tough. Especially so if the pastures have been overgrazed or are in poor condition. Pastures in poor condition are the perfect home for the rampant growth of weeds. Farmers face a difficult choice at this point. They can let the field be overcome by weeds and lose it as a grazing pasture or for hay production. Or, they can treat it and re-establish it. As you can imagine, the choice is an easy one for them. Manage it with a weed-killing and suppressing product, and put it back into action.

It’s Not Round-Up or Glyphosate

For once, Round-Up or Glyphosate is not the villain. This time it is something more insidious, and just as widely used. It is also recommended by the majority of Extensions and other Ag educational services. These chemicals are broadleaf weed killers that systemically kill while suppressing new growth for up to three years. They are highly effective products for those who use them. For farmers, they are well known as the only thing that can get a wasted pasture or hay field back. 

Enter the Picloram, Clopyralid, Aminopyralid, Aminocyclopyrachlor, Triclopyr, Simazine, and 2,4-D. 2,4-D is used often with Dicamba. Dicamba is the center of some massive controversy and legal action right now as I type. You can find products containing these chemicals at your local big box store, farm store, even on Amazon. Trade names in the United States for products include the following: 

Triclopyr: Garlon, Remedy, Access, Redeem, Release, Weed-B-Gone, Crossbow, and many others. It is one of the most common products used in the US.

Simazine: Princep, Simazine

Clopyralid: Stinger, Transline, Reclaim, Curtail, Confront, Clopyr AG, Lontrel, Millennium Ultra, Millenium Ultra Plus, and Redeem. Many US states have banned the use of Clopyralid. However, it is still available and the most effective product for eradicating Alsike clover.

Picloram: Grazon, Graslan, Surmount, Grazon Extra, Grazon Next HL, and Tordon. You’ll see it used in combination with products such as romoxynil, atropine, diuron, 2,4-D, MCPA, triclorpyr, and atrazine. Grazon Extra is an example. 

Aminopyralid: Grazon products such as GrazonNext, Milestone, Capstone, Chaparral, CleanWave, Forefront, Opensight, PasturAll, and Sendero

Aminocyclopyrachlor: Imprelis

2, 4-D: One of the oldest and most widely used defoliants in use. Over 1,500 products contain 2,4-D.

The Effects on You, the Home Gardener or Market Gardener

Shoveling healthy composted horse manure into the gardens

If you use composted manures in your gardens, and you’re not a farmer with livestock, you’re likely to be using compost from many possible sources including:

  • Bagged from a big box store
  • purchasing it directly from a farm
  • buying a soil blend by the truckload that already contains compost

You will have no idea if the compost contains manure from animals who have grazed on treated areas. Nor will you you know if they consumed forage products from treated areas. The only way to guarantee the safety of the compost is to know the compost. Know what you are getting from a producer who knows what they feed and grow.

In our case, we don’t feed forage products that come from outside sources unless verified. For example, we feed Standlee Alfalfa pellets soaked with meals for the horses. I have confirmed with Standlee that they do not treat their growing areas with these products. I feed alfalfa specifically because it is a broadleaf legume forage and not treated with these classes of herbicides. My hay, while not certified, is produced as organically as possible. 

Here on our farm, we also do not use chemical herbicides; however, in the interest of full disclosure, 2,4-D was used back in 2013 when we installed our riding arena. We have not used it since, but it was the reason I began to research this topic in the first place. 

The Effects of Killer Compost on Your Garden

These herbicides target broadleaf plants. You’ll likely see no effects for 2-3 weeks after planting in a garden with this contaminated compost. The plants will grow, and nothing will seem amiss. The herbicides’ actions will be seen in the nightshade family plants first, specifically the tomato plants. Plants that were thriving will begin to struggle, eventually wilt, and within days succumb to the action of the herbicide. Other plants in the garden will start to show similar signs within the next few days and weeks. 

To the inexperienced gardener, this failure might look like watering or fertilizing issues. They will add more compost, essentially hastening the plants’ death as they feed and water.

How To Test Your Compost

I highly recommend every gardener test their compost before using it. Plant a well-started tomato plant in your soil mix with the compost, or in the compost itself. Do this before you fill beds or top dress existing beds that have produced without issue. Tend to this plant as if it were in the garden, and observe it daily for at least three weeks. If no indications of plant failure result by three-week mark, you can be reasonably sure that the compost is safe. 

Why Killer Compost is a Persistent and Dangerous Problem

Killer Compost persists and continues to wreak havoc simply because gardeners, and farmers, are unaware of its affects. The gardener relies on nutrient-rich “black gold” to ensure bountiful harvests. The farmer relies on lush fields full of grasses to sustain their grazing animals and keep them in optimal health. 

Over the years, I’ve found that the majority of horse owners I have spoken with were not aware of this issue. They had no idea that this could end up affecting the composted manure they sell or give away. The same goes for the market farmers, farmsteads, and homesteaders who produce cattle, goats, sheep, and other livestock.

Controlling weeds in pastures and hay fields can be done without using the herbicides. It can be time-consuming and financially costly, so it’s not an option for many farmers and producers. I place no blame if the use of these broadleaf herbicides is necessary. However, it is up to them to be forthcoming and knowledgeable. Especially if they intend to sell or give away the composted manure generated on their farms. 

The home gardener, market gardener, farmstead, and homestead also needs to bear some responsibility. Ask questions and expect transparency when purchasing or taking free composted manure. Don’t be afraid to contact suppliers. A good supplier will welcome questions. If they don’t know and don’t seem alarmed or interested about this subject, look for another supplier. 

Where to Find Safe Compost

Your best resource will be a knowledgeable organic farmer local to you. As a producer myself, I am passionate about compost! I enjoy educating and talking to clients and readers about composting and how the process all works. Do your research and find compost that fits your expectations for quality and safety. Next, take the steps I mentioned above to test before you add it to your beds and gardens. 

If you find yourself facing a killer compost situation, please reach out to me to schedule a free consultation. I will share some specific tips on how to start the mitigation process as it applies to your situation. 

EPA Last revised March 30, 2007, EPA Chemical Summary: 2,4-Dichlorophenoxyacetic Acid (2,4-D) 

Please Note: The content on this site is for educational purposes only. This information has not been evaluated by the Food and Drug Administration. This information is not intended to diagnose, treat, cure, or prevent any illness or disease, and is not intended as a substitute for advice from your physician, veterinarian or other health care professional.

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Is Your Compost a Killer?


  1. Juliellen says:

    Such good information that I had not considered. Thank you!

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