Using cardboard in home landscapes and gardens has become a popular topic on social media. However, this practice dates back to 1944, when Ruth Stout introduced an organic, no-dig gardening method. Her approach gained popularity for creating healthier, more productive gardens with lower costs and a smaller environmental footprint. Over time, this evolved into what is now widely known as the “lasagna method,” often recommended for use in raised beds.
Today, cardboard has regained popularity as an affordable and effective weed barrier and a composting ingredient. While advancements in research have deepened our understanding, the question remains: is cardboard as safe and effective as claimed?
The controversy regarding the use of cardboard in landscape or garden beds centers on two primary concerns: penetration of water and oxygen, and potential soil contamination. Cardboard and similar paper products, when used as sheet mulch, are known to interfere with water penetration and oxygen exchange in the soil beneath, especially if the paper product is waxed. Paper sheeting blocks photosynthesis, which requires sunlight, making it an effective weed and grass suppressant. However, this same blocking characteristic also slows oxygen and water transmission. Keeping the cardboard moist can help with the needed moisture, but in a garden, the uptake of nutrients also requires oxygen in the topsoil layer.
Contamination of the area where cardboard is applied is a second major concern, particularly for organic landscapes. Contamination usually involves non-biodegradable and/or chemical substances. Additionally, some cardboard products are high in cellulose, which may attract termites. The risk is higher if you live in an area where these insects are present.
The popularity of cardboard in landscaping has also led to researched solutions and alternatives. Depending on your soil type and seasonal precipitation, reduced water penetration can be addressed by adding a drip line underneath large areas of cardboard and applying mulch on top to keep the cardboard wet. As this process can take 6–10 months, laying the cardboard in the fall yields an area free of weeds by spring. Your envisioned project can begin once the mulch and cardboard are removed. This minimizes cardboard contaminants in your soil, as it takes 1–2 years for cardboard to fully break down.
If you are a serious organic gardener, avoid the risk of cardboard contamination by solarizing large areas using clear plastic sheeting to kill weeds during the summer heat. Success can be achieved in just 2–3 months of summer heat. Alternatively, to avoid typical cardboard contaminants, use shipping boxes that lack ink, labels, and dyes. Remove any tape, avoid glues and waxed surfaces, and ensure the cardboard has not been treated with fungicides or prohibited substances, such as, e.g.,“Forever chemicals”.
Should you need to mulch smaller, targeted areas, consider other types of mulch as recommended by the University of Idaho Extension office. If you have a large garden or field crops, biodegradable plastic sheeting is commercially available. While not yet as cost-effective as cardboard, manufacturing improvements continue to lower the price.
While the decision is ultimately yours, a little research might lead to an easy, effective, and affordable way to suppress weeds and create a healthy, thriving base for your raised garden beds and landscape areas.
