The sunflowers sound like a good idea-- they would be tall when the sun is most intense, and not there in winter and spring when the sun is less intense. If clumping bamboo is evergreen here and always tall, that sounds a less desireable option.

If you could do a trellis, maybe something like Red Ripper peas on the west and south would be good, too.

Alas, I've no direct experience with your problem-- I'm still veggie gardening in big yard buckets that can be moved under trees in the summer.

Good luck with whatever you decide!

I have a cedar tree to the east and the South west of me. It is a real life saver in the summer. I think the arbor is a good idea. A fence of vine will make shade that does not over hang once it gets large. And it will be there fairly quickly. I am always having to clip branches off the cedar trees. They keep growing. Imagine that.

Is it really possible to get too much sunlight? I didn't think that could ever be a problem. Now, I can understand too much heat, and that leading to drying out the soil.

Maybe adding mulch (more mulch)?

Older post, but I do think you can get too much sun, especially since that leads to too much heat. Most veggies need 6hrs of sun, but you can easily get 8-10hrs in the summer. If you could keep it sunny from 8am-2pm, and shaded at some level after that, you get enough light for production, and keep it cooler in the afternoon. I use raised beds, and have shade cloths for each bed. I pull them back some to only shade in later afternoons. It's not perfect, as the heat killed about everything here last year. Heck, even our cedar trees are dying faster than I can count.