Have you had problems with soil disease in your vegetable gardens? Have you spent more time pulling weeds in the soil than you have pulling veggies off the vine? For some of you out there, battling issues with your soil can sure take the fun out of gardening real quick! If you are one of these struggling gardening souls, and you’ve never heard of solarization as a technique to help give you a clean slate of soil, I really think you’ll want to read on.

In layman’s terms, solarization is a method where you use the energy of the sun to “cook” the undesirables out of your garden soil. Huh? It really is this simple! Solarization basically neutralizes your soil and gives you a level playing field to start with in your gardens.

Soil Solarization: Why and When

Studies have shown that gardens which have been solarized have less issues with soil-borne diseases and insects and  competition from weeds for nutrients in the soil. Studies have also shown that solarized gardens also tend to yield more produce than those that haven’t been. Might you now be interested in this intriguing process?  

Summer is the best time for solarization. For one, the hot rays of of the sun that shine on San Antonio are intense and we need that heat for the process. For two, many gardeners decide to sit summer out and wait for the fall gardening season. You can harvest the last of your spring veggies to enjoy, then pull up last season’s plants and start the solarization process in your empty gardens. Oh, and for three, solarization takes around 30 to 45 days to work (if you can do 60, two months, that’s even better).

Doing this process sometime in summer will give your soil the time needed to have you garden ready and waiting for compost and new veggies come fall. Remember, fall tomatoes need soil that’s ready mid to late August! Just saying, it’s not time to procrastinate if you want to try solarization.


Clear plastic and sunshine makes solarization work great.

6 Steps for Successful Soil Solarization

1. Remove old plant material and pluck out all the weeds that you can by hand as well. I like to add an extra step right off the bat and thoroughly mix some Happy Frog’s Jump Start 3-4-3 Fertilizer or Espoma’s Biotone Soil Activator deep into the soil. This step is not mandatory, but these products contain active soil microbes that benefit from solarization too, meaning an added boost to the overall health of your soil, so why not?


2. Water your garden soil. Thoroughly. For the solarization method to work, the soil must be moist throughout and covered after wetting it. P.S. This does not mean to drown your soil, just a very thorough watering.


3. Cover the entire garden with a clear sheet of plastic. The thicker the plastic, the better it works. (Clear plastic shower curtains are an ideal thickness to strive for, one layer of Glad Wrap won’t do it.) For solarization to work, the plastic must be clear because clear plastic allows the heat of the sun to pass through and will also trap the heat in the soil. Remember that old experiment using a magnifying glass to burn holes through a piece of paper or unsuspecting ant? (No? Just me?) It’s kind of like that. The power of the sun streams through the plastic and heats up the soil to annihilate disease and insect organisms and would-be weed seedlings. This is what solarization of the soil means.

NOTE…Black plastic won’t work because it absorbs the heat before it can get to the soil where you need it. Clear plastic allows the sun to do its thing.


4. Secure the clear plastic tightly on all edges and corners of the garden. The goal is to “seal” in the heat and energy from the sun, as well as the moisture from when you soaked your garden. Get creative here with your measures for sealing the plastic; use something that won’t allow the plastic to lift off and flutter around on a windy day. Some old clamps, cinder blocks or wood plans around the edges could work. Solarization doesn’t have to be an expensive process.


5. Relax and wait for the solarization process to run its course. Waiting 30 days to remove the plastic is good; 45 days is better, and 60 days is best. This truly is a sit back and wait type of thing. There will plenty for you to do during our maintenance gardening months through summer; you just won’t have to worry about your veggie gardens until fall prep.


6. Get picky about the products you add to your newly solarized soil. Once you’ve completed the solarization of your gardens you will have “clean” soil that is ready to be enriched further with quality organic ingredients. Get your compost from reliable sources (ahem, us). Free may sound good at first, but you might not know what has been mixed in there. When using your own compost, make sure you haven’t been tossing in diseased plant material or lawn clippings full of weeds or you might find yourself in the same situation as before the  solarization.

Of course we will still offer you all the fungus, insect, and weed control you’d like, but if you’ve battled these things often, maybe this method is worth a shot? Give your veggies, and more importantly, your soil, a healthy start by trying solarization. Oh, for you die hards that grow veggies through San Antonio summers, rock on! We wish you the best! Whether you try solarization or not, in the words of a favorite band, “Here comes the sun, here comes the sun, and I say, It’s all right.”

~The Happy Gardener, Lisa Mulroy