Ah ha outdoors,i reckon you could go as big as you want,i did an outdoor in
cut off 10 gallon drums i dug holes to put them in placed gravel at the bottom
drilled load's of holes in the drums,i gave them fish and bllodmeal manure
and basically checked on them every now and again,to make sure they were
wet enough and scattered some manure pellets around them,one thing i will
say if you can get some chicken wire put it around the base to keep critter's
away and a sprinkling of builders lime around the base of each pot will keep
snail's and slugs away,outdoor is great it's natures way,ask the guy's in the
outdoor growing thread they really no their shit and are generally a very helpful
bunch of people!!!!
Hope this help's and may you get a bountiful harvest!!!