A Warning About Straw

Claude Monet used straw (or is that hay?) for art. We use straw to catch chicken droppings!

Straw is a very inexpensive and useful material for composting, mulching and animal bedding (we use it for all of these purposes). If you use it for mulch you’ll probably get some seeds that will germinate, but I’ve never found it to be a big problem in a small vegetable garden. I get my straw from the feed store, but you can often get it for free from yuppies on Craigslist who have bought it to give their parties the Hee Haw ambiance we enjoy 24/7 at the Homgrown Evolution compound. If you buy it from the feed store remember to ask for straw, not hay. Hay is green and a lot more expensive. You feed hay to your horses.

But one warning from my friend, permaculturalist David Kahn. It’s tempting to pick up bales that stores have used after Halloween, but make sure they weren’t treated with fire retardant. Fire retardant has some nasty chemicals in it you don’t want in your garden. When in doubt, just go to the feed store–straw it ain’t expensive!

Addendum 10/27/09: Reader Polyparadigm raised another potential issue with using straw in your garden or compost pile: halogenated pesticide/herbacide residues. Clopyralid is an example–while banned for use in lawns in many places it’s still allowed on hay and grain crops . All the more reason to grow your own mulch and carbon materials if you can–don’t throw out those fall leaves! Here’s what Polyparadigm says:

“I’m glad I read through to the end! I was thinking this would be a warning about clopyralid and its close cousins. Which bears some mention: Halogenated pesticides aren’t broken down by any but a few soil organisms.

Clopyralid and aminopyralid mimic the hormones in broad-leaf plants, causing them to grow un-evenly and die from wrong-facing, crinkled leaves and other symptoms. Grasses are un-affected, so fields of grain and lawns have been sprayed with this sort of chemical, as a cheap way of keeping broad-leaf competitors at bay for a few years.

These chemicals have a half-life of 11 months in hot compost, and are often applied at such high rates that certain plants won’t grow in garden soil dressed with finished compost from a mix of sources, if one of those sources is a treated lawn or field.

A quick bioassay will test for this in straw: peas sprouting from soil mixed with that straw will look deformed if the field that grew the straw was treated. Browns of a similar texture from a source you know to be clean should probably be used for a control group.”

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12 Comments

  1. How timely – today our whole house smells like straw – we bought a bale of it for the chicken bedding, but I chopped up a bunch yesterday and then pasteurized it in big canning pots on the stove to grow Oyster Mushrooms (pleurotis) on. We’ll see how that goes… one thing I can tell you with authority, simmering straw at 170 degrees in pots on the stove for an hour makes your house smell like a barn (in the good way?).

  2. I’m glad I read through to the end!

    I was thinking this would be a warning about clopyralid and its close cousins.

    Which bears some mention: Halogenated pesticides aren’t broken down by any but a few soil organisms.

    Clopyralid and aminopyralid mimic the hormones in broad-leaf plants, causing them to grow un-evenly and die from wrong-facing, crinkled leaves and other symptoms. Grasses are un-affected, so fields of grain and lawns have been sprayed with this sort of chemical, as a cheap way of keeping broad-leaf competitors at bay for a few years.

    These chemicals have a half-life of 11 months in hot compost, and are often applied at such high rates that certain plants won’t grow in garden soil dressed with finished compost from a mix of sources, if one of those sources is a treated lawn or field.

    A quick bioassay will test for this in straw: peas sprouting from soil mixed with that straw will look deformed if the field that grew the straw was treated. Browns of a similar texture from a source you know to be clean should probably be used for a control group.

  3. >thanks for the heads up

    You’re welcome! I wish I’d phrased it slightly differently: the half-life figure is just for one chemical, there’s probably lots of variation among them.

    >All the more reason to grow our own compost materials!

    I sort of agree.

    I could also see it as a reason to culture fungus, like Tom and Lyanda are doing: button mushrooms fed a steady diet of clopyralid-laced straw will likely find some benefit in boosting their production of the enzymes that would metabolyze it, the same way humans make more lactase or amylase after a few generations of diets that offer some benefit. The time spent in the fungus growing beds should make the straw safer than if a similar time was spent in a compost pile.

    And economic and political pressure from backyard gardeners is an important thing for agribusiness to face. If a market for straw exists, it might influence growers away from long-lived pesticides. Even if the money is negligible, the publicity is really important.

  4. Mushrooms are bioaccumulators, though, so extreme caution should be taken in what is used as substrate for mushrooms for human consumption. Like, organic straw only!

  5. I picked up some wheatstraw at the local racetrack in Berkeley and used it to start oyster mushrooms and I have been suspicious that it was tainted with some type of herbacide because the beans and peas and lettuces I seeded it with were small and sickly and died quickly. A few years ago I bought some ricestraw and I grew lots of tomatoes on it without problems. In both cases the nutrients used were the same (Miracle Gro). I would add my voice to those who say beware of the possibilities of contamination with pesticides in straw bales because unfortunately the cynics who are out to make quick money in straw bale gardening are often dishonest and will do anything to turn a buck.

  6. Pingback: Straw Bale Gardening : See Sheila Run

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