I learned in the Organic Gardening Yahoo Group that most straw and manure is contaminated with herbicides and that the cheapest way to test is to grow some beans or peanuts.
I tried to follow the instructions at Bioassay Test for Herbicide Residues in Compost: Protocol for Gardeners and Researchers in Washington State and here is what I got:

10/3/10 herbicide test results

On 10/3/10 each pot got 3 beans (from a soup mix) and one peanut

On 11/1/10 I needed to make room in the greenhouse, I took the pictures and planted the beans and peanuts outside.

  • The first row is straw with a bit of  local virgin dirt. It grew one grass, nothing else.
  • The second row is Gro-Well mulch with a bit of  local virgin dirt.
  • The third row is aged horse manure with a bit of local dirt. One of the peanuts all of a sudden died.
  • The fourth row is a neighbor’s garden soil (not organic, with fertilizer pellets).

The garden soil definitely did best and the horse manure also did ok.


The Grow-Well mulch supposedly did NOT contain sewage sludge (as their “organic” mulch), but we don’t buy any Gro-Well products anymore because they are as vile as Monsanto. This was the last of the Gro-Well mulch and we bought organic mulch in Vegas at Star Nursery on Easter for $27/yard (We paid $45/yard for the Gro-Well mulch).
A few weeks ago we stopped to talk to a landscaper feeding his wood chipper in Kingman and we now have a source of FREE wood chips, pine needles and of course lots of native plant chips.  We just got our 2nd load and that’s as cool as it gets.

We had purchased the straw at the feed store on Stockton Hill (Kingman), primarily for adobe.  I asked about herbicides and the guy didn’t know.

We used some of the straw as mulch in August, thought the light color would reflect the summer heat.  I’m sure glad we didn’t use a lot, mostly by our grapes after I planted peas and beans.  I wondered why next to none germinated in the part with the straw and now we know why.

Here’s an excerpt from Leslie’s excellent page about herbicides:

Residues of Picloram, Clopyralid or Aminopyralid Herbicide Create Killer Compost

Minute concentrations of picloram, clopyralid and aminopyralid, as low as 1 ppb (parts per billion), can be lethal to sensitive garden plants such as peas, beans, lettuce, spinach, tomatoes and potatoes.
Most pesticides, including herbicides, break down quickly in the composting process. Picloram, Clopyralid and Aminopyralid do not. These chemicals are

  • Easily absorbed by plants.
  • Remain chemically stable and intact in both live and dead plants.
  • Do not breakdown substantially in animal digestive tracts so contaminate manure, urine and bedding with residues.
  • Breakdown very slowly in composts and soils with an estimated half life of 1 – 2 years.
  • Affect sensitive crops at very low concentrations – 1-3 ppb.

The only way to handle this potential threat is to keep materials contaminated with picloram, clopyralid and aminopyralid out of your garden in the first place.

Trade Names Please

When you’re talking to a farmer supplying hay, straw or manure asking about picloram, clopyralid and aminopyralid is probably not enough. You’ll need to ask about specific trade names of the herbicides.
These herbicides are sold under the following trade names.

  • Picloram – sold as Tordon, Access, Surmount, Grazon, and Pathway.
  • Clopyralid – sold as Curtail, Confront, Clopyr AG, Lontrel, Stinger, Millennium Ultra, Millenium Ultra Plus, Reclaim, Redeem, Transline.
  • Aminopyralid – sold as Milestone, Forefront, Pharaoh, Banish.

Where and Why are Picloram, Clopyralid and Aminopyralid Used?

These herbicides are used to control broadleaf weeds such as Canada thistle in the following situations

  • Turf such as golf courses.
  • Pastures for animals such as cattle, horses and other animals.
  • Grass family crops such as wheat, barley, grass hay.
  • Transmission line rights of way.
  • Ditches along roads.

Two things make these herbicides a popular choice. First, they are persistent so do not need to be applied often. Second, they appear to have little to no effect on the health of animals and people.

How Do Picloram, Clopyralid and Aminopyralid End Up in your Garden?

There are three main paths that could bring these herbicides to your garden.

  • Contaminated Mulch materials – hay, straw and grass clippings.
  • Contaminated Manure and Bedding from livestock fed crops treated with these herbicides. Ask whether animals have been fed hay harvested from ditches or transmission lines. Avoid those that have.
  • Contaminated Composts made from contaminated hay, bedding, grass clippings and manure.

Ironically, the people most likely to wind up with these materials in their gardens are organic gardeners.

What Crops are Affected?

Even very small amounts of picloram, clopralid and aminopyralid – as little as 1 ppb – can negatively affect sensitive plants. Dow, the manufacturer of these herbicides, claims that only a few plants are affected. The average home gardener may beg to differ. Sensitive plants include:

  • Legume family – including lupines, peas, beans and clover.
  • Compositae family – including daisy, aster, sunflower and lettuces.
  • Nightshade family – including tomatoes, potatoes, peppers and eggplants.
  • Umbelliferae family – including carrots.
  • Many other vegetables and flowers.

Sensitive plants are exposed to these herbicides develop cupped or fern like leaves and twisted stems. They do not produce well, though in theory the crop is safe for you to eat.

What to do if your Garden is Contaminated

We are very lucky that around here the ditches are graded (not sprayed with herbicides) and you can collect cow pies guaranteed NOT to be contaminated with herbicides from cows roaming the desert.
However, we DO get sprayed regularly with unidentified substances, see Sunset chemtrails in the Joshua tree desert.