When Michelle Obama converted part of the White House lawn into a garden six years ago, she made it look easy. And lawn killing certainly can be easy, depending on your game plan. It can also be a difficult, frustrating failure.
The First Lady's strategy was detailed in a recent story on The Atlantic's website, written by the son of the farmer who assisted her. Organic soil from a nearby farm in Pennsylvania was trucked down and dumped into wooden frames on the White House lawn.
This is a perfectly good tactic, if you have the resources and want to garden in raised beds. Assuming you do, it is without question the quickest way to convert lawn into garden.
For demonstration gardens, or for gardeners with limited space or little tolerance for mess, raised beds can be a great system. But for large plots of land, a ground-level garden comes with more options, and less carpentry involved.
The easy way is to cover the lawn with plastic and wait for it to die. A more common approach is to dig up your lawn, pulling out the grass as you go. Even if you use a tiller, this is backbreaking work that usually fails, because roots will inevitably stay in the ground. Grass roots are extremely hardy and will re-sprout. Meanwhile, all the plant material that is removed from the soil represents fertility leaving the garden. To be fair, the pulled-up grass could be composted, but then there is still the matter of the roots remaining in the soil.
Another bad tactic is to cut and remove the sod where you want to plant. As with digging the grass, enough of the roots will likely be left behind that the lawn will return. And by removing sod, you're not only losing the potential fertility of the grass, but the actual fertility of the topsoil bound in its roots. And you'll need to import dirt to replace the sod and bring the garden up to ground level.
So unless you're building raised beds, tarping is the way to go. After a few months under the summer sun, the grass and roots will have been transformed into worm poop, and your lawn will be a garden.
The only downside to tarping is you have to plan ahead—and be patient. While it involves very little active work, you have to wait about 10 weeks. If you're hoping to turn your turf into tomatoes this summer, it's not going to happen (unless you ignore my advice, use the shovel and do battle with an endless parade of grass shoots from your tomato patch).
The news that you can't—or at least shouldn't—garden in your lawn this summer might come as a disappointment, but here's a consolation prize: When you pull off that plastic in late summer, it will be the perfect time to get ready to plant garlic.
Garlic is planted in fall, sprouts in springtime and proceeds to shoot up quickly and impressively. At the time of this writing my garlic is knee-high, and gearing up to produce bulbs this summer. If your winters are mild enough, you could also plant hearty greens, like kale, in your former lawn, and let them overwinter.
Whatever you choose to plant in the lawn's wake, the cause of death will remain the same. Black plastic is ideal. White plastic reflects too much light and won't heat up enough, while clear plastic can get hot enough to kill soil bacteria and send the bugs crawling to deeper, cooler quarters.
Black plastic is widely available, usually in rolls, at hardware or garden stores—if not, it can be ordered. You want it about 2-4 mils thick ('mil' being the unit of thickness used to measure tarp thickness).
Before laying down the tarp, I like to dig a narrow trench around the perimeter of the garden plot that I'm envisioning. I toss the shovelfuls of sod into the middle of garden spot. This step isn't necessary, but it helps me visualize the garden to come.
Eventually, the converted lawn is going to need some kind of border to ensure the surrounding grass doesn't re-colonize its former turf. This barrier, like lawn edging, will be easier to install once the grass is dead. But keep this future step in mind.
On a non-windy day, place your plastic on the future garden spot. If the plot requires multiple pieces, try to cut the plastic as few times as necessary, producing as few pieces as possible. The pieces should overlap one another by at least a foot or two; don't allow any cracks between the plastic sheets.
As you lay out the plastic, cover it with objects to weigh it down. Almost anything will work as a weight, including bricks, blocks, boards, buckets and bicycles, as well as items that don't begin with "B."
It's especially important to weigh down the outer edge—fill the trench with heavy items—and along the edges where two pieces of plastic come together. You want to make sure no wind gets under the tarp.
Then, sit back and let the microbes, pill bugs and worms do their thing. You may be losing lawn, but hang onto that lawn chair. You'll need it for sitting, while you sip something cold, as your lawn dies a slow and glorious death.