Just throw a layer or two of cardboard down below the dirt (making sure there are no gaps between pieces).

Works great at killing weeds, but doesn't kill beneficials (worms etc). And actually earthworms LOVE decaying cardboard, so might even add more :)

I did this last year with the 9 raised beds I built, and it has worked fantastic. And I only went 10-12 inches, not a full 2 feet like you are planning.

Also you make a comment of "I plan to do a bed that's raised maybe 2 ft, so not too much additional soil" - just so you know that's a LOT of soil depending on the size of your beds :) Unless there is a reason to go higher (convenience so you don't have to bend over, building over concrete etc....), I personally think 12 inches is more than enough, and my garden this year is proving it!

Good Luck and have fun.

Thanks! Cardboard would be easy.

I guess 12 in would work, the soil underneath is just so bad (and probably has some lead) I wanted a good barrier. I have a huge mound of 'cheap" soil used for filler, was going to use that for the first foot then "good" soil mixed with compost for the next foot. Maybe that's not necessary.

A question, have you had this soil tested?

Its really hard to know what to do with a piece of ground if you don't know what is actually wrong with it. :-)

Additionally, unless you make them with waterproof bottoms like giant pots, raised beds require more water than in-ground plantings. Since you said you're in a drought do you have the water for this? Is there any likelihood of water restrictions cutting off that water?

I won't be doing any plantings until we're out of this drought. We tend not to have decades long droughts like CA, just yearly ones. I do have a garden now that I water, but it's in ground and not doing great (too much sun). Yes, there are water restrictions but they don't apply to vegetables, just landscape.

And no, I haven't bothered to have the soil tested, since I don't really plan to use it. It's heavy clay and a pain to work with. Part of the reason to do a raised bed is so that it's easier to work with better soil (I have laid soil on top of the other garden area, but didn't raise it with a border). The other reason is because I plan to basically turn a large portion of the back yard into a garden eventually, and the way the area is laid out, raised beds at assorted angles with pathways between will work better/look better than in ground. Will start with one bed at a time though.

The bermuda in this area scares me. It will NOT go away, it's nearly impossible to get rid of (especially without chemicals). I spray bermuda with round up and it still comes back.

I would NEVER plant anything where bermuda is/was. I have a pile of compost that is easily 4 feet tall and 8 feet or more long. I laid down cardboard and newspaper pretty thick below it, and then had it dumped in place.

I have bermuda that has grown up right in the middle of the pile, it grew up through all this and straight up 4 feet!!!

all i can suggest is take a look at our presentations there maybe some ideas there for you.

len

Here is a link that might be useful: lens garden page

Here are some pictures of the area I'm considering:
This spot gets a fair amount of shade, maybe too much, but with summers at 100F+ for weeks on end, maybe that's needed?
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Note the car won't be there....this is where the rye was.
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There was bermuda where my current garden is, and though I've had other issues with that space, I haven't had any problems with the bermuda coming back there.

as you say with summer being so hot a shaded area need not be so bad, just depends on how much shade most vege' type plants like around 5 to 6 hours sun. in hot summers in the morning is the best so long as they get shade say from around 9am or 10am onward.

raised beds with the use of say up to 8" layer of mulch will keep the root runs of the plants cooler and help contain moisture so the roots will be well catered for. we find plants then will cope with the stress of some sun better.

len