How High Can Raised Beds Be?

Q: I am working to create permanent raised beds in my garden. I have been told that raised beds should not exceed twelve inches high because the soil becomes too hot and dry. 

A: Raised beds do dry out a little faster but that is because the soil in them is typically loose and well-drained, not because the soil gets hot. I commonly see raised beds where the sides are eight inches high and the soil has been loosened four inches beneath that. This gives a plant rooting area twelve inches high, which is plenty for vegetables.