weed prevention in raised bed for vegetable garden

Asked January 12, 2019, 3:25 PM EST

I plan to build 4 raised beds for vegetables in my old garden which was over run with weeds last few years. I like to use only organic material for weed prevention. Several on-line videos suggest to lay down cardboard (from store or moving boxes) inside the raised bed before filling in top soil. This method can suffocate weeds while allowing water and roots to penetrate through. The cardboard should decompose overtime. I am a little uneasy about it. Do you recommend such a method to prevent weeds in raised bed? Do you see any issue if using such method? Would appreciate your expert opinion. Thanks very much.

Anne Arundel County Maryland

2 Responses

Cardboard makes great weed-smothing mulch, though it takes much longer to decompose than newspaper(s). Some gardeners put it on top of beds in the fall, to prevent winter annuals from getting started in fall and growing all winter.

We're not sure why the cardboard would be necessary, though, in the bottom of a new raised bed planter. Since the planter will have several inches of soil added to fill it, that soil should prevent growth of weeds--unless you have some well established perennial weeds there, such as pokeweed with its large fleshy root. Deep soil would prevent seed germination. Soil, and maybe a few layers of newspaper, will kill small perennial weeds.

We'd recommend that you dig out any huge-rooted perennials anyway before you build and fill your raised beds.

You may also want to cut off the tops of any living or dead weeds that have seeds. If you bury these weed seeds deeply, they will not germinate now. But, many seeds remain viable for years, and if/when you turn the soil in your beds, you will turn them up so they can then germinate.


Thanks very much for your fast response. Your answer makes excellent sense. I think i’ll skip the cardboard inside my new raised bed, which I plan to fill with ~8 inches of clean top soil. After planting, I’ll mulch on top with organic mulch. This should cut down weed problem. again, thanks very much for excellent suggestion.

Margaret Wu