Can a raised bed be lined with plastic..?
Raised Bed Gardening
Certified GKH Gardening Expert
If there are an appropriate amount of drain holes, then yes, but I do not recommend this. Fabric is a much better alternative, that will allow water to drain freely. There are specific landscape fabrics for this purpose. They can be relatively cheap depending on how much you need, and will save you a lot of trouble that will come with a plastic bottom.