Garden Weed Control: My Soil Solarization Experiment

I had some major weed issues this last garden season!

This last spring I incorporated two trailer loads of horse manure into my garden to add organic matter and nutrients to the soil.  While I love what it did for the texture of my predominantly clay soil, there were two pitfalls to my efforts.  First, the manure had residual water soluble herbicides, most likely from treated hay, that my source and I didn't realize were present.  (I highly recommend you read the full story here before making a decision for or against using manure in your garden.)  Second, and this I anticipated, the manure brought in an abundance of weed seeds that grew with great delight (as you can see in the picture above) until I got a handle on them.

There are several ways to eliminate weeds.  I used two of them this summer by mulching and physically pulling the weeds, and another was inadvertently added to my garden with the manure, herbicide.  While herbicides have their place, in general, their use is not preferential in a home garden since it can harm your plants and can collect in the produce we then eat.  A forth method of weed control is called soil solarization.  This method uses the energy of the sun to super heat the soil and cook any weeds and seeds present.  It is this method that I am experimenting with this fall and coming spring.

The literature I read recommends using clear plastic to cover the weed infested area during the hottest part of the season for 4-8 weeks.  I decided to take this concept and see if I could adapt and gain from it before spring planting next season, so over the weekend I took a few minutes to cover my garden with 4ml black plastic.  I am hoping to utilize the heat absorbing properties of black to trap the indirect solar rays we have yet this fall and again after snow melt in the spring to get the soil warm enough to significantly reduce my weed problem next season.  As my husband pointed out, this will inhibit any water penetration from snow melt, so it is not something I will want to do on an annual basis, but worth a try for this year.  I'll let you know how it goes...

I found this University of California site on Soil Solarization for Gardens and Landscaping to be very complete and helpful as I researched what I wanted to do.  Check it out if you are looking for more detailed and complete information on soil solarization. 

Happy Gardening! :)

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