yes,but it depends on your design,materials,potting mix,ferts.etc

Eathbox holds about 2 cubic feet of potting mix and is considerably larger than 5 gallons. I think it is about 15 gallons, it seems to me it holds about 65 or 70 quarts, last time I counted.

It is indeed larger than 5 gallons! But it seems to me it is less than TEN gallons, which is what I was going to use for TWO tomato plants.

A simple calculation taking the specifications (29"L x 14"W x 11"H) from Earthbox site gives more than 16 dry gallons:

29x14x11=4466 cubic inches

Using cubic inches to dry gallon converter gives:

4466 in� = 16.6144 gal(US Dry)

Some volume should be subtracted because of the water reservoir at the bottom of the container. On the other hand, Earthbox instruction recommens making a 2" mound of the potting medium, so 16 gallon should be very close to the actual volume.

I had a similar concern, so I am trying four pepper plants in one and two determinate tomato plants in another. I have used the original self watering containers from gardener's supply for years, and they work great with one pepper plant in each.