How deep should my raised beds be?

[Waxman]

It's a newb question I know but can anyone humor me? Going to be growing some plants in 4x8 beds just want to know how deep I should make them I was thinking 12".

Also one more question I'm trying to figure out what strains would do well in my climate I live in central/northern AZ. According to the site in the link below im living in zone 3 or 4 closer to 3 in my opinion.

http://cals.arizona.edu/pubs/garden/az1169/

 

[_tessarecting]

18", 24" if its very hot

 

[BAKED_BEANZ]

and if its very hot , mulch the shit out of them . a lot of people won't know this . but if your grounds too hot your plants will stall and flower early . you may think your watering enough you don't need it wrong .

anyway mulch has far greater value anyway . just a heads . enjoy