Did the Solarization Experiment Work?

In early summer, we solarized our front yard. You can read the full post here. By using the clear plastic to trap the heat of the sun, the goal was to essentially cook the soil, killing any weeds and weed seeds present. I was hoping this was the magic non-toxic  solution for my constant battle with Bermuda grass. So now, about 3 months later, you might be wondering, did it work?

First, let’s review how the actual solarization process went.

We spent one weekend tilling, watering, and laying out the plastic. The plan was to leave that plastic in place for 4-6 weeks. After that, my plan was to remove the plastic, and throw out buckwheat as a cover crop, which would add some nutrients in the soil and provide some cover from windblown seeds. Then, a month later (buckwheat grows uber fast), I would wack that down, then layer compost on top of that, and plant a low-water native landscape that I had designed.

Here’s how it actually went. The plastic started to break down after about 2 weeks, with tiny holes from sticks poking though, and slits appearing. We made some attempts to use duct tape to seal the splits, but more and more appeared each day. By the end of the month, we gave up.

The plastic only lasted about 3 and a half weeks, not nearly the 6 weeks I had hoped for. It was still too early (ie, middle of summer and therefore f’ing hot) for me to throw out my cover crop seeds, so I went with my next best option for covering up the soil. My dear friend, cardboard.

I reformatted my plan (you have to be flexible with plans when you’re dealing with gardens). I would cover the space with cardboard, leave until late September, however ugly it might be, but it was both shading out any potential weeds and preventing traveling seeds to sprout. Then, I’d spread a layer of horse manure, throw out winter cover crop at the end of October, then plant my native low-water landscape in the spring.  As I pulled away the shredded plastic, I would lay out sheets of cardboard. It took about a month of weekend trips to the furniture store, bike shops, and appliance store dumpsters to get enough cardboard to cover the area we solarized. I used large pieces, and made significant overlap, to prevent spaces for the weeds to grow back.

I got as far as covering the area with cardboard before finding out we were going to be moving at some unforeseen time in the near future. I can assure you that a front yard covered in boxes (at least I put them all label and text side down!), weighed down with bricks and assorted rocks, was not aesthetically pleasing. My dear neighbor from across the street kindly described it as a ‘neat modern art’ installation. I didn’t want to put out soil (expensive), but I didn’t want to pull the cardboard up (exposing ugly dead weeds and dirt). So I revised my plan AGAIN (and people think I’m not flexible….HA!) and started covering it with wood chips. This made it so it looked decent for potential house buyers, and it also created a good base for the next people to start landscaping.

So did the solarization attempt actually do anything?

When I pulled up the plastic, there were some tiny bits of Bermuda grass still green and growing. It wasn’t as prevalent as before, but it was still there. I pulled what I could before I laid down the cardboard, and most was easy to pull. They weren’t deep, which makes me think they were segments or seeds, brought to the surface from the tilling. I saw no signs of the other weeds, like the sow thistle or the plantain.

Now, a good 4 months later, with a thick layer of cardboard and mulch and we’ve had rain, I still see no signs of the ‘other weeds’. There is Bermuda creeping in from the edges, which was expected, as I didn’t go all the way to the edge of the street pavement or onto the neighbors property. I don’t see any signs of it emerging from the interior mulch. I do have, however, have bulbs pushing though, which surprised me. I had a healthy population of paper-whites, daffodils, and sporaxis that was also growing in the ‘lawn’, but I was sure that the rototiller would have chopped them all up or they would have baked from the solarization.

Would we try solarizing again? Maybe.

That’s what it comes down to, right? I think the plastic tore so quickly because the front gets so. much. sun. Add the reflection of the blacktop from the road, our driveway, and the house- it freaken bakes out there. The plastic expands and contracts with the heat and the cooling of night, and small sticks would poke though. If we made the plastic looser or had a softer surface it laid on, it might have done better. We put some of the plastic out in a section of the back yard that gets less sun than the front, and it didn’t tare nearly as quickly. We also didn’t till or water the soil under it, so it didn’t do much. It seemed to work great for the ‘lesser’ weeds, but not perfect for the Bermuda. So would we do it again? It depends.

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