Weeds can be a persistent nuisance, sprouting almost anywhere they find an opening – between paving slabs, in flower beds, or across lawns. While many gardeners turn to boiling water, white vinegar, or baking soda, a horticultural expert has proposed an unexpected alternative: reusing old cardboard boxes to prevent weed growth.
How cardboard blocks weeds
Chris Bonnett, horticulturalist and founder of GardeningExpress, explained that leftover cardboard offers an eco-friendly way to recycle boxes while helping the soil as the material naturally decomposes. Laying cardboard over problem areas suppresses weeds by blocking out sunlight, which weeds need to grow.
For troublesome outdoor spots, cut a section of cardboard to fit the area and remove any plastic tape or labels, as these will not break down naturally. Then place the cardboard flat on the ground, ensuring it covers the entire affected area and is firmly secured to prevent any gaps.
Overlap and cover for best results
If only smaller pieces are available, Bonnett advised overlapping them by around 15cm to stop weeds creeping through the edges to reach sunlight. Once positioned, add a layer of mulch or compost on top – this secures the cardboard, improves its appearance, and helps retain soil moisture.
The expert noted that this method allows the cardboard to decompose naturally within the garden. It should remain in place to keep weeds at bay while slowly breaking down, enriching the soil with organic material.
A natural alternative to chemicals
Bonnett advocated for this technique over chemical weedkillers, warning that such products can create "problems" elsewhere in the garden. He added: "After a few months, the cardboard will begin to decompose, benefiting the soil as brown matter, helping to create a healthier growing environment for the rest of your plants."
