Raised bed ques

[TightenUp]

If building a raised bed on concrete how deep should the bed be?

[fortyonenorth]

I have about 10 planters 18"-22" deep. They are on a concrete garage roof. I raised them with 2 x lumber so there is about 1 1/2" clearance at the bottom for drainage. They've all performed very well for tomatoes. If you're growing other veggies exclusively you could probably get away with 12-16".

[coloken]

You may get all kinds of answers but.
I have heard of 6 inches being enough for vegetable.
My own are on concrete , made from 2 by 10 (old water beds). and grow 6 foot high tomatoes with no problem.
So my answer would be 8 inch minimum 10 inches better and 12 inches would br very nice.
I should add that my beds are 4 foot by 8 foot. Smaller planters and boxes could be different.

[lakelady]

I see people growing tomatoes in bags of compost which are not very high; this leads me to believe the roots will grow horizontally if t here isn't enough room vertically. Could be wrong, but it's what i've seen.

[TightenUp]

thanks for replies. i assume the deeper the better but also the more money. trying to find the middle grounds.

got a lot of cedar plus the 1-1-1 method to buy. every time i make a decision i have another one in front of me.

anyone have a good website for cedar(or raised bed kit?) locally its expensive.