TL;DR
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A two-year trial involving the University of Wyoming and USDA Western SARE found cardboard mulch reduced weed coverage and increased yields for some vegetables by as much as 97%. A Gardening Know How writer also reported a weed-light bed and a personal best harvest after using cardboard, but that home test was informal and does not establish that cardboard caused the result.
A two-year trial involving the University of Wyoming and USDA Western SARE found that cardboard mulch reduced weed coverage and increased some vegetable yields by as much as 97%, according to Gardening Know How, whose writer also reported a strong personal harvest after trying the method. The findings suggest cardboard can be a useful weed-control option for vegetable beds, though the writer’s own results were informal and the source does not provide crop-by-crop trial data.
The trial was conducted at Sweet Hollow Farm in Victor, Idaho, in collaboration with the University of Wyoming and the USDA’s Western Sustainable Agriculture Research and Education program. It ran across different crops and seasons over two years at a site described as having a short growing season. Gardening Know How reports that some crops increased in yield by up to 97%, but does not identify which crops achieved that figure or give the underlying yield measurements.
The source also reports 15% weed coverage in cardboard-mulched beds, compared with 45% in beds managed with traditional tilling. It does not specify the measurement method or provide further statistical details. Separately, the article’s writer says they covered a vegetable bed with old cardboard during the summer and assessed it in October, reporting that it was 95% free of weeds and produced their best-ever harvest. That is a personal observation, not a controlled experiment.
The article recommends using brown, uncoated corrugated cardboard, removing tape and shipping labels, and overlapping sheets by at least six inches where persistent weeds are a concern. It describes the trial’s method as placing four to six inches of compost over the cardboard before planting, with seedlings set through holes in the layers.
Potential Gains for Vegetable Beds
For gardeners, the reported results point to two practical benefits: less weed growth and the possibility of improved yields. A mulch that blocks light may reduce the need to weed or till, while the report says cardboard helped keep soil moisture more consistent in the writer’s informal comparison with an uncovered bed. The source does not quantify water savings, labor reductions or costs.
The findings may be relevant to growers looking for low-cost ways to reuse clean packaging, especially where weed pressure is high. But the reported yield increase of up to 97% applies to some crops in the trial, not necessarily every vegetable or garden. Local climate, soil, cardboard preparation, compost depth and planting practices could affect results.
cardboard mulch for vegetable beds
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How the Cardboard Trial Worked
The article describes the research as a USDA-funded, two-year trial involving the University of Wyoming and Western SARE. The test site was Sweet Hollow Farm in Victor, Idaho, which the report identifies as a Zone 4 location with a short growing season. Different crops were grown across seasons, and the comparison cited was between cardboard-mulched beds and beds maintained with traditional tilling.
For the trial, the report says researchers used two layers of corrugated cardboard to create a barrier against persistent perennial weeds such as field bindweed. They covered it with four to six inches of compost and transplanted seedlings through openings. The article’s writer used one layer at home and says it worked well in that bed, but those differing methods and conditions mean the personal account should not be treated as a replication of the trial.
“My veg bed is not only 95% free of weeds but I’ve enjoyed my best-ever harvest.”
— Gardening Know How writer
uncoated corrugated cardboard for gardening
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Limits of the Reported Results
The source does not include the trial’s full report, crop-specific results, sample sizes, statistical significance, or detailed methods for measuring yield and weed coverage. It is therefore unclear how broadly the up-to-97% yield increase applies or whether the same outcome would occur in other regions and growing conditions. The article also does not explain whether results differed by crop or season.
The writer’s own harvest report is subjective: the source gives no weights, harvest counts, comparison plot, or details about other changes to the bed. The claim that cardboard kept moisture more consistent is based on informal comparisons and a moisture meter, not a reported controlled test. The guidance about avoiding coated cardboard, inks, labels and adhesives is presented in the article, but the source does not provide specific testing data for every packaging material.
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What Gardeners Can Test
The source describes no announced follow-up research or next trial milestone. Gardeners considering the technique can follow the reported preparation steps: use clean, brown corrugated cardboard; remove labels and tape; overlap edges against persistent weeds; and cover the cardboard with compost before planting. The article suggests testing questionable cardboard with a drop of cooking oil: if it soaks in, the writer says it is more likely to be uncoated; if it remains on the surface, avoid using it in the bed.
Anyone trying the method can record yields and weed coverage and compare mulched and unmulched areas under similar conditions. Such observations would help distinguish a personal result from a repeatable effect; the source gives no guarantee of a particular harvest increase.
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Key Questions
Did cardboard mulch increase vegetable yields in the trial?
Gardening Know How reports that some crops increased by as much as 97% in the two-year trial. The source does not name those crops or provide full yield data, so the figure should not be read as a typical result for every vegetable.
How much did cardboard mulch reduce weed coverage?
The report gives weed coverage of 15% in cardboard-mulched beds and 45% in beds managed with traditional tilling. It does not provide the measurement protocol or statistical details.
What kind of cardboard does the article recommend?
It recommends brown, uncoated corrugated cardboard and advises removing tape and shipping labels. The article warns against glossy or water-resistant cardboard and highly pigmented inks.
How was cardboard used in the reported trial?
The article says researchers used two layers of corrugated cardboard, covered them with four to six inches of compost, and planted seedlings through openings. The writer’s home test used one layer.
Does the writer’s harvest prove cardboard caused the result?
No. The writer reported a nearly weed-free bed and a personal best harvest, but the account was not a controlled test and did not include measured yields or a matched comparison plot.
Source: rss
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