Sunday, July 24, 2011

When 'Organic' Gardening Goes Horribly Wrong

I have a friend who's had some trouble with his tomatoes and peppers this year. I never seem to have a camera handy when I'm out at his garden/farm, but I can say that the leaves on most of the tomato and pepper plants in most parts of his garden are narrow and twisty with weird pointy parts.

At first, I thought the problem might be a virus (it definitely wasn't a fungal or bacterial infection), but it seemed that the problem might also be caused by herbicide residues in the soil. My friend uses horse manure, but he was a little doubtful when I said that I thought herbicide residues might be causing the problem. He ages that manure in huge piles for a full year, and he's never had this problem before (in more than 20 years of using manure as his main source of organic matter in the soil).

To find out for sure, I did the experiment described in various places online. I took some of his soil home with me, mixed it half & half with potting soil, then divided that into three pots. I did the same thing with soil from my own garden so I'd have a control to compare the results to.

Then I went to one of those big box stores and bought a four-pack of Big Boy tomatoes. I planted two in his pots, two in mine, and planted bean seeds (five each) in the other two pots.

In the bean pots, four germinated in my pot and only one in his, but they seemed to be mostly ok after coming up.

After three weeks, this is what the leaves on my tomato plants look like:

And these are the leaves on his tomato plants:

I'm pretty sure this means that herbicide residue is the problem, and it turns out that the problem showing up most often at the County Extension office this year is this exact problem -- damage from herbicide residues. In most instances, the damage is worse because people have used grass clippings from lawns sprayed within the last month or so right on their gardens as mulch. At least my friend's source of herbicides has sat around for a full year, giving it more time to break down and disappear.

The real frustration here is that people are trying to do the right thing -- using local amendments to improve their soil (my friend) or local mulches (others) to reduce evaporation from the soil, saving water, and to reduce the need for weeding. These uses also keep organic matter out of the landfill.

I brought my experiment to an organic gardening class I was co-teaching with the leader of the Plant-a-Row-for-the-Hungry garden, and it turned out that one person who showed up had already had the damage-from-grass-clipping problem.

Another had bought some hay to use as mulch in her garden that has always been managed using organic-approved practices and never had any big disease problems. She and her husband had brought leaves (thankfully in plastic bags, so spores weren't getting loose all over the place) from plants in her yard to show several disease problems that seemed to have arrived with the hay.

They had been told that the hayfield had never been sprayed, and I had a huge moment of doubt about that, but after more thought this seems totally possible. If the field hadn't been sprayed, it probably had a lot of weeds in it. Some of those weeds were probably in the same families as the now-infected garden plants (including the tomatoes). Weeds could easily be carriers of diseases that her garden had never before been exposed to.

This is all one big cautionary tale. I am now thinking about ways to get more organic matter into my garden without actually bringing it in from the outside, because the outside is looking pretty untrustworthy. I've grown winter cover-crops before. The vetch that I grew wasn't especially attractive, or all that easy to dig back into the soil in spring, but I am thinking about trying that again.

I've also read in Dick Raymond's "The Joy of Gardening" that in plots where he had experimented with growing two crops of edible legumes (beans, peas, not vetch) in the succession with other crops, the soil was great. He had dug in all the crop residues from the two legume crops. His method calls for growing a lot of peas.


  1. Wow, that is quite a bummer. It's a good experiment you did to see what was causing the problem. There are so many obstacles in organic gardening.

  2. meemsnyc, I think what's frustrating for most people is that they aren't doing anything new; something has changed somewhere else along the way.

    For the herbicide damage, I think it's that some of the newer chemicals take longer to break down than the older versions.

    From the perspective of a person who is trying to control broad-leaf weeds in the yard or field, that longevity is a good thing. For gardeners, that is a very bad thing.

    In years past, the chemicals would be broken down and relatively harmless to the growing plants by the time the clippings or manure were applied, but not anymore.

  3. A plant hormone or hormone analog would still be active at very low concentrations and could last years in the soil if it is artificially produced and bacteria or fungus don't have a way to break it down. My guess is that it might be a contaminant of a herbicide product and thus not tested for.

  4. Marc, That would be a major bummer for my friend, because it looks as though the production of the plants is being affected in a bad way. It would be awful if the problem lingers for years.

    The little bit of consolation for my friend is that not all crops are affected as strongly as the tomato-family crops, and that parts of his farm/garden haven't had any manure additions in the last few years, so those areas are probably fine.

    Thanks for stopping by and leaving the note. I hadn't thought about contaminates in the herbicides, but that is a possibility. Hope your little family is doing well and managing to keep cool enough in the Mid-Western heat! -Amy


Related Posts Plugin for WordPress, Blogger...