With summer approaching, it’s time to start focusing on outdoor projects and leave the indoor projects for the winter. Even if the weather doesn’t want to cooperate. The previous owners of my house had a section of the back yard, about 1500 square feet, sectioned off to grow grass including an underground sprinkler system. When I moved in to the house it had been unoccupied for a while and the weeds had taken over. I tried growing grass where it used to grow but haven’t had success.
The problem, the low water grass (buffalo grass, blue gamma, etc) I’ve tried growing can’t compete with the weeds. I refuse to use chemicals to kill the weeds and I’ve tried manually cutting down the weeds down and pulling them out but it hasn’t been effective enough (especially against the dreaded goat heads aka Tribulus terrestris).
I’ve discovered a chemical free method of eliminating weeds on a large scale called solarization. It uses transparent plastic directly on the ground to bake the soil and will kill seeds. It’s possible to cook the soil 6 inches deep and at 125 degrees ore more. The University of Arizona has a good article on the process for use in Tucson (also see Wayne Schmidt’s Solarization Page) and should adapt to New Mexico.
The timing for installing the plastic is good right now, it has just rained giving the ground a good soaking and the spring winds died off long enough to install the plastic. My first try was using 108 square feet of 1 mil painters drip cloth. The thinner the plastic the better the sun penetrates but 1 mill is too thin for this application. Even though I had cut down the weeds even a little bit of plant materials was able to puncture the plastic. Smaller sections of plastic are harder to manage than larger sheets.
I was able to find 500 square feet 4 mil plastic sheets at the local WalMart (as much as it pained me to have to enter the place). It wasn’t cheap at a cost of $20 per roll. I could have probably put a ad on craigslist and found some plastic sheeting for free but I have a limited window to install it.
The installation of the plastic went well. I used bricks to hold the plastic down while I laid it out. I then dug a trench around the perimeter and used the dirt to seal the edges. I used two sheets and overlapped them about 6 inches using bricks and landscape staples. It’s important that air cannot get under the plastic sheeting so the moisture and heat stays under the plastic.
I’m not planning on growing grass in the entire area where grass originally grew, only about 1000 square feet so two sheets should be sufficient. Since I will be out of town for most of the summer the ground should be well cooked by time I get back. I will try to make regular soil temperature readings during the summer.