Sheet mulching can be used to convert turfgrass to landscape beds and it helps retain moisture for new plants.
Rylee Jacobs is an intern in SAWS Conservation.
Sheet mulching, often called lasagna gardening, is a simple and effective method for improving soil health while keeping weeds at bay.
Instead of hauling compost or digging up turf, this technique allows you to compost directly on-site by layering cardboard, newspaper and organic matter over a project area – often when establishing new landscape beds. Over time, these layers break down, enriching the soil and improving the soil health below.
There are many methods of sheet mulching, with some processes incorporating compost over the course of several months to improve soil structure and fertility. As the layers decompose, they attract earthworms and beneficial microbes, further enhancing soil vitality.
But the simplest and quickest versions of sheet mulching can be used to convert turfgrass to landscape beds by blocking sunlight and suppressing weed growth to the grass below. In addition, it helps retain moisture for new plants.
Rethink landscape fabric
With the abundance of synthetic landscape fabric in home improvement stores, many homeowners automatically turn to it for short-term weed control. It’s designed to block plant growth from below while allowing water to pass through for other plants in a landscape bed. But it can be problematic over the long term, as leaves and other matter break down on top of the fabric. These layers become a new layer of soil and a breeding ground for weeds whose roots eventually penetrate the fabric. Over time, the fabric itself breaks down, allowing even more weeds to penetrate.
While these issues happen over time, for many garden enthusiasts the most annoying problem with the fabric is that they’re difficult to pierce with shovels — making it harder to plant new plants.
Cardboard: A biodegradable alternative
Cardboard offers a sustainable, cost-effective and shovel-friendly alternative to landscape fabric. Both standard cardboard and corrugated fiberboard can be used, though they vary in thickness and layering. And it’s unusually abundant these days, thanks to the popularity of online delivery services.
Cardboard paired with hardwood mulch decomposes naturally and supports soil life, making a terrific biodegradable alternative to synthetic weed fabric:
- Prepare the cardboard
Use large, non-glossy pieces with minimal ink. Remove all tape, staples and stickers as these won’t decompose and can interfere with soil health. - Clear the area
Use a string trimmer or other hand tools to eliminate large weeds, grass clumps and debris from the area you plan to mulch. Pay special attention to the edges of the bed to prevent future weed intrusion. - Lay the cardboard
Place the cardboard directly on the soil, overlapping the edges generously to block weeds from sneaking through gaps. Use two layers if the cardboard is very thin, or one layer if it’s thick. - Add mulch
Cover the cardboard with a 2- to 3-inch layer of shredded hardwood mulch. This top layer holds the cardboard in place, retains moisture and adds nutrients as it breaks down. - Water the area
Lightly water the mulch to help settle the layers. The moisture speeds up microbial activity in the soil beneath and helps the cardboard adhere to the soil. - Monitor and maintain
Over time, wind, weather and wildlife may disturb the mulch and gaps may appear. Just scoop it back into place. Cardboard breaks down over time but just continue to monitor and reapply mulch as needed.
Sheet mulching with cardboard has been widely practiced in San Antonio in recent years as an easy way to convert portions of the landscape from turfgrass to drought-resilient landscaping.
By choosing biodegradable materials and embracing passive composting, you can create a garden that’s more resilient, lower maintenance and rich in life. This method offers a practical and eco-friendly path, whether you’re just reclaiming a weedy patch or preparing for an upcoming WaterSaver Landscape Coupon project (coupons are coming in September!).
