This year for the first time I have had to temporarily cover my vegetable garden with shade cloth, what I am using now is just lengths of different strength shade cloth that I have laying around but when I build my new and bigger Vegetable garden I am going to buy new stuff. The plan is to have strained wires spaning across the entire Vegetable garden and have the shade cloth stretched between the wires and attached to them with metal rings so that the shade clothe can slide back and forth with ease when they are needed. I can get lots of 70% shade cloth for a good price when compared to 30% shade cloth so I would like to use the 70% stuff if I can.
to give you an idea of what I am up against here is a short list of some of the plants I have had to cover so far,
sweet corn, tomatoes, potatoes, chillies, Jerusalem artichokes, capsicums, eggplant, dill, comfrey, pumpkin, squash, melons and sunflower.
In nature, bigger fruit/nut trees provide the shade that you are talking about.
The leaves of mulberry trees for example are edible as a vegetable and it also bears edible fruits.
You can cut it every year, if it get too big. It only bears on new(current year) growth.
You can grow you regular annual/vegetable right up to the tree trunk, if you really wanted to use up every sq inch.
They is a long list of trees that you might consider most of them are just 10ft. http://www.onegreenworld.com//index.php?cPath=1
You can also find cultivars that are more tolerant of your (hot, sunny, dry) conditions.
These guys might have what you are looking for. http:www.nativeseed.com