And so to removing lawn. The good news: Water savings and new design options await. The bad news: It's a lot easier to put in grass than to take it out. In evolutionary terms, grass is a pioneer plant that can establish almost anywhere. Its roots have tenacious survival mechanisms. It can root in a crack in the sidewalk. It's quick to set seed. Those seeds sail on wind, hitch rides on animals, and insinuate themselves into the soles of shoes. Some grasses don't even need seed to spread. They clone themselves from the roots. In other words, when you decide to kill grass, you're up against evolution itself. And you will fail. So the art in removing a lawn is choosing the grass-removing techniques that fail best while building up a new ecology that favors successor plants.
The four most widely recommended lawn removal methods sound like chapter headings from a murderer's handbook: chopping, poisoning, cooking, and smothering. Whichever one you choose, the process starts the same way: Cut the grass as short to the soil line as possible. String trimmers can be rented cheaply from lawnmower shops and do a good job. Dispose of cuttings and seedlings, then, 24 hours before you plan to start work, water the lawn deeply enough to penetrate the root zone four to six inches.
And all four methods also all end the same way -- mulching the uncovered ground and wetting it sufficiently that the newly bare soil and mulch topping begin to commune. It's sensible to lay in enough wood chips to be able to mulch the project area to six inches deep. This will not all go down at once, but in two separate three-inch applications, the first immediately after you remove the lawn, the second months later.
None of the four methods completely address the most important place all gardeners should remove lawn, which is underneath trees. So we have a fifth approach for lawn removal, something of a hybrid of chopping and smothering, to help Southland gardeners kill their lawns but spare the tree.
And so to the four schools of de-lawning:
1. Chopping. If it's a large area, you may want to rent a sod cutter or hire a contractor to do it for you. If some cursory exploratory digging reveals less lawn than a grass-choked tangle of failed weed cloth, construction debris, rocks and old sprinkler heads, short of dynamite, you may need to turn it with a pick, pull out obvious weeds, rubble and trash, then rototill as a second pass. Wear protective gear. However, you will still have a long way to go. Grass loves nothing more than having its seeds plowed under. Bermuda grass also appreciates its regenerative roots being cut up in small pieces by the till blade, so you will have to start killing the lawn again once you've fished out decades of junk.
With small- and medium-sized spaces in lots where historically trash service didn't include burying it, chopping grass out by hand can be effective using only shovels and a needle nose pick. The virtue of starting this way is that you can work incrementally, one area at a time, and get to know the ground as you work.
Bermuda grass is especially tough. To tackle it, loosen the roots with the needle nose of a pick then pull the grass out by the rootball, teasing as you go. The more diligently you sort the roots from soil, the less recurrence you will have. Some gardeners sift the soil. This will catch more roots and rocks but it will risk making the soil hydrophobic (ever seen water run off really dry, fine dirt instead of soaking in?) and make reaggregtion of an absorbent soil slower down the line. Safety note: Never swing a pick over your shoulder unless you want a self-administered spinal tap. Pick up the tool and help it drop, getting the tool to do as much of the work as you can.
Sod lawns that were rolled out like carpets are relatively easy to cut up and roll up again.
2. Poisoning. Facilities managers and restoration ecologists with more acreage than manpower frequently use herbicides on large spaces. Horticulturist Bart O'Brien, manager of Tilden Regional Park near Berkeley, used glyphosate -- the active ingredient in Roundup, to transition his former Inland Empire garden from turf to native garden. His tips: It can only be done in hotter months on warm season turf types such as Bermuda grass that are semi-dormant in California winters. After the first application, the treated lawn should be watered to spur growth from surviving roots and seeds. O'Brien warns that glyphosate should not be applied near existing trees or shrubs. Be sure to observe the manufacturer's instructions.
3. Cooking. Covering lawn with plastic sheeting captures the heat of the sun to bake the lawn. It is best used on open ground in thermal belt inland areas during the hottest months of the year. It should never be used in areas around trees where it will interfere with absorption of rain and damage shallow feeder roots. As these UC Davis management guidelines suggest, it is also good for sterilization of mulch that may contain pathogens or weed seeds.
4. Smothering. Also called "lasagne mulching" or "sheet mulching," this has long been a favored method of Missy Gable, former program manager for the UC Davis California Center for Urban Horticulture and now director of the UC Master Gardener Coordinators. In 2014, a project called "The Crescent Farm" at the Los Angeles County Arboretum and Botanic Garden in Arcadia used it in a test plot on an established lawn with Bermuda and the equally dreaded kikuyu grass. They also tried digging the grass out. The project's design consultant, Leigh Adams, reports sheet mulching won so conclusively that "there was no comparison." When grass did recur, Adams adds that it came out easily because of the newly arable nature of the improved soil.
Sheet mulching saves much of the labor of digging out grass. It avoids the toxicity of glyphosate. It is often more wholesome for soil culture than solarizing. But it entails more preparation. The prep starts with scrounging for cardboard. Make sure you have enough to cover 125% of your project space (you'll need the extra for trimmed areas and overlaps.) UC Davis gardeners recommend using the largest cardboard boxes that you can find -- even going to bicycle and appliance stores. Do not use laminated boxes. Remove any plastic cord, tape, labels and staples.
Before laying out the cardboard, Adams recommends digging turf out from a six-inch-wide margin around the borders to create a clean border against which to line up the flattened box edges. Once this is done, lay the cardboard piece by piece over the targeted grass so the edges overlap ("like roof shingles," Adams says). Then with fine sprinkling, and avoiding any sheeting of excess water, soak the cardboard. Once it is fully damp it's time to spread three inches of mulch over the top.
After the mulch is down, water it again so the wood is also damp. Then every week or so, continue wetting the area just enough to avoid any drying and warping of the cardboard. As grass recurs, pull it and tamp down disturbed earth to avoid colonization by grass and weeds. Your lawn is now beginning a process of turning from grass to a rich soil complex that will support the succession garden.
5. Removing lawn around mature trees. Lawn should never have been planted under trees, not least because the turf gloms the tree's water while string trimmers damage the trunk and mower blades damage the roots. Perhaps worst, sprinkler water collecting at base of the trunk and in branch crotches foments rot in summer heat, then termites move in to perform the coup de grace. Instead of turf, trees should have the ground around the base of their trunks clear of anything but their own leaves and mulch to help prevent evaporative losses in the Southland's hot climate. So, especially everyone, listen up: Whatever landscape scheme you choose down the line, get rid of that lawn beneath your tree. It's wrong, wrong, wrong.
Using glyphosate or solarization in this situation won't work unless you want to kill the tree. Chopping and sheet-mulching are the only two safe methods for under-canopy lawn-o-cide. After you give the lawn its crewcut and broadcast watering in the first step, coil a slow drip soaker hose around the base of the tree starting at the outer canopy line (the outermost point reached by the branches) and ending two to three feet from the trunk. Connect it to a garden hose on a slight pressure. Adjust pressure so no water is leaking at the hose bib, but droplets are steadily beading the length of the soaker coil. Deep water the tree overnight.
The next day, coil back up the soaker. Hand dig the turf out from around the trunk to the canopy line taking care not to damage any tree roots. Lay down cardboard, soak it, then mulch. Keep any excess soil, cardboard and wood chips at least a foot away from the trunk to avoid crown rot. Before mulching, return the soaker hose to its concentric pattern under the canopy, puncture the cardboard at four- to six-inch intervals with a shovel tip to increase water penetration. Drive small stakes in the ground to hold the soaker in place and to mark its path. Then mulch over the cardboard and hose and continue with the sheet mulching instructions in Step 4, with the additional action of hooking up the soaker once a month to deep water the tree. If you're using existing sprinklers to periodically dampen the mulch, do not let the water hit the trunk. Better yet, dampen the mulch yourself using a hose and conserving nozzle.
A note on mulch. A good source, usually free, is to have a local tree trimmer with a grinder deliver it to you. This may mean accepting a four-ton load, so make sure that there is space in your driveway or parkway the equivalent of about two to three cars to hold it. Do not allow it to be dumped against the trunk of a tree or around a hydrant. Also make sure that the ground wood came from healthy trees that merely needed pruning or removal, not from a diseased specimen. You might also check your city's sanitation department website for giveaways of municipal mulch (you'll need a pickpup truck to go get it). Calblend Soils in Irwindale is one of many landscape supply companies that delivers bulk mulch more economically than buying it in bags at a garden center. If you're bad at math, simply enter the term "mulch calculator" into an online search engine for help figuring out how much you need.
Another note, this time on patience. There are no links or helpful tips here about planting a new garden immediately after removing a lawn because the easiest place for lawn to recur will be in the holes that you dig for your new plants, which you then water. Apart from summer vegetable plots, new gardens should also not be installed in the Southland outside of fall and winter months when, weather permitting, rain will water them in. So don't go for instant conversion. Treat the interval between getting rid of your lawn and the advent of the next planting season as the most important thing you will do for your garden, which is building a healthy new soil complex. You'll know it's working when you see birds and lizards move in to start worming.
Next installment: Shaping the new space.