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Do Peanut Shells Make Good Mulch or Compost?

Q. What do you think of peanut hulls as mulch? A local plant that makes peanut products gives them away. I used them last year in my garden and they were effective at controlling weeds (though I did get a few volunteer peanut plants); and they don't seem to carry any disease. What will they add or take away from the soil? Enjoy your show greatly,

    ---Rick in Box Springs, GA (near Columbus)

Do you think peanut hulls, which are available in my area, both whole or ground up, would be a better or worse mulch than wood chips? Thanks for your help!

    ---Michelle in the very southeastern corner of Alabama (Daleville)

This will be my third year trying to be a successful tomato grower. I am making compost according to your instructions and don't use any chemical fertilizers. A gardening friend has told me that decomposed peanut hulls make an excellent compost for tomatoes. Is this true? It seems to me that the peanut hulls would be similar to wood chips or bark and "wood" (pardon my pun) therefore be a No-No. Thank you for your program and all your advice,

    ---Stan in Phoenix City AL (100 miles southwest of Atlanta)

I am a novice gardener and would like to know if large quantities of peanut hulls would be desirable for garden mulch or as compost ingredients. A potential source is nearby and I noticed that peanut hulls were listed as an ingredient in a tomato container mix I used successfully years ago. Thank you for all your great info; I currently support two public radio stations!

    ---Christopher in York, PA (West of the Susquehanna and North of the Mason-Dixon Line)

A. As I expressed out loud on a recent show, I had a nagging thought that someone had warned me something about peanut shells. Luckily we didn't need to trust my memory any further than that, as I can file with the best of them and quickly found the references that our unsurpassed unpaid fact-finding fanatic Charles Younger sent me last September.

Following the reference trails, I found many extension agents repeating the same warning—don't use peanut shells as a MULCH in the South as they can harbor Southern blight and other fungal diseases and may contain {quote} "nematodes", which could only in this circumstance refer to the nasty Southern root-knot nematode and not the beneficial nematodes we good little organic gardeners rely on for controlling grub, flea and other pest problems.

NOW, all of the warnings I found are suspiciously identical to each other; and one of the delicate dances I have to do every day is try and evaluate whether warnings like this mean 'it's likely to happen' (as in wood and bark mulches breeding nuisance fungi) or 'it could theoretically happen' (and extension agents often feel an obligation to cite every bad thing that could possibly happen). BUT several of the extension articles also linked to longer articles on Southern blight that had photos of the disease and I would not wish such detestation on anyone.

Luckily, all of the references I've found—and an article we did on locally available bulk organic matter in ORGANIC GARDENING magazine back in '94—recommend peanut shells as an excellent compost pile ingredient. And so I say to organic gardeners North and South, East and West: Compost your peanut shells!

Original research we did at the magazine also found that (probably because they're a legume), peanut hulls are surprisingly Nitrogen rich. They're also brown as opposed to green, which even I find confusing (welcome to my world, kids—you try and figure this stuff out!), so I'm going to punt here and just say to shred them well, wet them down and mix them up with a lot of other raw ingredients. But no matter what, they shouldn't do anything bad as a compost pile component.

Now we get to mulch. Rick in the wonderfully named "Box Springs, Georgia" (which must lie just underneath the town of Mattress, GA) notes in his email (which, like most of your emails, asks the relative wisdom of something you've already done) that he saw no disease problems using a peanut shell mulch, strongly implying that he had seen the same warnings. The fact that you tried something and nothing bad happened the first year is no guarantee of its wisdom, and I can't get those blight pictures out of my mind. So it is with some regret that I suggest our Southern listeners compost their shells and find another mulch—like the finished peanut hull-containing compost, which all sources agree is no longer suspect.

And what of our listener in York, PA—who even points out that he is North of the Mason-Dixon line? (But not by much, I'll note here.) Some of the extension warnings about mulch specify that they only apply to the South; so can he use his locally available bulk peanut shells as a mulch?

I might. They are nitrogen rich and not all carbon, so they will cause none of the problems of wood mulch and sawdust, like plant starvation and nuisance molds. And the fungal diseases they might harbor are not a problem in a Northern climate. Now, is it impossible for them to occur in the North? Heck, no; you get a summer as hot and wet as they get in St. Louis or Al-bama and spores are spores. But they wouldn't overwinter; they'd be a one-season problem.

So I just might use them as a mulch—above that Mason-Dixon line, of course.