One of our roles as Master Gardeners is to answer gardening questions from local residents. Since watering restrictions have been in place, one of the questions I frequently get asked is how to remove long-established hybrid bermudagrass, tall fescue, or combination grasses and weeds lawn. My first response is "It isn't easy; it will require time, probably money, and some manual labor."
One of the easiest and least expensive methods of turf removal is the sheet composting method. First, cut the grass (weeds) as short as possible. Second, cover the area with cardboard (used boxes or purchased rolls) or newspaper (10-12 layers), making sure the edges overlap a substantial amount so no sunlight can get through. Next, water, cover with a layer of compost, and lastly, cover with at least 3-4 inches of mulch. You can cut holes in the cardboard to plant individual plants or wait until the cardboard decomposes and dig planting holes for your new plants. This method adds organic matter to the soil, requires minimal labor, and does not require removal and disposal of turf. It takes a long time for the grass/weeds to disappear completely and cannot be used on steep slopes.
Two years ago, I watched neighbors use this method on their hybrid bermudagrass front lawn. After covering the area with layers of cardboard and mulch, they dug holes and planted drought-tolerant shrubs. (The drip irrigation system had to be installed under the cardboard and mulch.) Today, it is a beautiful water-wise yard without a runner of bermudagrass in sight.
Still not being a total believer in the method, I wanted to try it for myself. Last fall, my mother-in-law moved to a smaller apartment with a ragged, unkempt combination of weeds and crabgrass for a lawn. This was the perfect spot for my experiment! With permission from the landlord and help from a grandson and other family members, we hoed out the biggest weeds, mowed the remainder down to the runners and went dumpster diving for cardboard. We ran irrigation tubing to where I wanted new plantings to go, and covered the entire area with flattened cardboard boxes, spreading 4-5 inches of mulch over all. Then, the rains came. I checked the area weekly, a few sprigs of crabgrass poked through where I had not overlapped the cardboard enough. They were easy to remove with a hula hoe. In March, I dug holes in the cardboard and planted Nandina (Heavenly Bamboo), Loropetallum (Razzleberry shrub), Heuchera (Coral Bells), and Ophioppogon (Black Mondo Grass). And, still more rains came! I was able to keep the crabgrass under control by hand pulling every couple of weeks. In our hot summer months, all the new plants are growing nicely, no weeds or crabgrass. I am a believer!
For other turf removal methods, visit the Master Gardener website at http://cetulare.ucanr.edu and click on Master Gardener and search grass removal methods. You will find lots of practical advice.
Now, to follow up on my love of cardboard. In the December 2016 issue Garden Gate magazine, I found an article about gardening uses of cardboard. Number one use: weed barrier, unwanted grass removal. I was hooked. Another suggestion was to use cereal boxes and milk cartons as pots for seedlings. You can plant the boxes directly into the soil as most are compostable.
Still, more suggestions include: Keep copy paper box lids or similar shapes in your car to carry plants home after a trip to the nursery. Folded lengths of cardboard make great kneeling pads while gardening. And, a flattened piece of cardboard can be used to transport weeds, dead stems and other trimmings to the compost or yard waste can. The cardboard slides easily over grass or concrete. If you like to grow potatoes, a large heavy-duty packing box, at least 18 inches deep, filled with compost and potting mix, can be used as a raised bed for potato growing. At the end of the season, cut the box open, remove the potatoes and compost the rest.
The good news is cardboard, especially the brown corrugated kind, is one of the least processed cardboards and thus is good for composting. Shred or tear it into small pieces to add "brown material" to your compost pile. There is not much nutritional value, but it is good to dry bulk for the decomposition process.
Cardboard can be used by a gardener in many ways, is compostable, and recycling is great for the environment.