Raised beds / planter boxes on concrete?

[MotherForkinShirtBalls]

I've a long strip (20m x 2m) outside the back door that gets a lot of sunshine. Up til last year there was a shed on it so its a flat (but uneven) concrete slab. Since it gets so much sunshine I thought it would be good for fruit or veg but I absolutely don't want to go to the hassle or expense of digging out the concrete to put on beds. I was looking at some wooden planter boxes online but all the pics have them on what looks to be grass/soil so I don't know if it would be a runner to put them on concrete. I'm concerned that drainage would be the main issue. Or something else I don't know about...

I did something similar on our (concrete) front garden but to grow flowers and shrubs in. As you say, drainage is an issue - in our case we had higher than normal beds made to make sure there was enough soil and root room, and we put lots of rocks at the bottom too, to help with drainage.

Just drill some holes in the bottom

I grow all my veg in big pots on a paved terrace. Your wooden planters are just big pots, at least they will be with some drainage holes