Can I put cardboard over allotment weeds?

Yes. Plain cardboard laid in an overlapping double layer and covered with suitable organic mulch can suppress grass and many weeds when starting a no-dig bed. Remove tape and staples, avoid shiny printed card and check that coverings comply with site rules.

Build a continuous layer

The RHS advises overlapping sheets so weeds cannot grow through gaps. Wet the cardboard if you intend to plant immediately, then add a thick layer of well-rotted organic matter. The cardboard is a temporary barrier; the mulch holds it down and forms the growing surface.

Cardboard is not a reason to ignore persistent weeds. Watch for regrowth around edges and through planting holes, and remove it before it becomes established. Do not leave loose sheets exposed where wind can carry them across the site.

Use the right material

Choose plain brown corrugated card with labels, plastic tape and metal staples removed. Do not use waxed, heavily coated or food-soiled packaging. If you cannot cover the cardboard fully with appropriate mulch, wait until you can make the bed properly.