On open ground, nothing but a layer of plain cardboard to smother the grass. In a bed deeper than about 18 in, fill the bottom with logs, branches and leaves: in a 4 × 8 ft bed 24 in deep, a 12 in layer of them saves about 35.8 cu ft of soil, 18 bags of 2 cu ft. Skip the gravel layer: in a bed on soil it does not improve drainage.
A 5 gallon grow bag takes about 21 litres, or 0.7 cu ft, of potting mix once you allow for settling, so one 2 cu ft bag of mix fills 2 of them. A 10 gallon bag takes about 1.5 cu ft. Use potting mix, not garden soil.
Twelve inches suits most vegetables, and it takes about 35.8 cu ft of soil in a 4 × 8 ft bed (18 bags of 2 cu ft). Six to 8 in is enough for lettuce, greens and herbs; tomatoes, squash, potatoes and long carrots do better at 18 in or more, or in a 12 in bed over loosened ground.
Frequently asked questions
What should I put in the bottom of a raised garden bed?
On open ground, nothing but a layer of plain cardboard to smother the grass. In a bed deeper than about 18 in, fill the bottom with logs, branches and leaves: in a 4 × 8 ft bed 24 in deep, a 12 in layer of them saves about 35.8 cu ft of soil, 18 bags of 2 cu ft. Skip the gravel layer: in a bed on soil it does not improve drainage.
How much soil do I need for a 5 gallon grow bag?
A 5 gallon grow bag takes about 21 litres, or 0.7 cu ft, of potting mix once you allow for settling, so one 2 cu ft bag of mix fills 2 of them. A 10 gallon bag takes about 1.5 cu ft. Use potting mix, not garden soil.
How deep should a raised garden bed be for vegetables?
Twelve inches suits most vegetables, and it takes about 35.8 cu ft of soil in a 4 × 8 ft bed (18 bags of 2 cu ft). Six to 8 in is enough for lettuce, greens and herbs; tomatoes, squash, potatoes and long carrots do better at 18 in or more, or in a 12 in bed over loosened ground.
This site uses a small amount of storage so it works, and with your permission, to understand which pages are useful. Read the cookie policy or the privacy policy.