Hard to give advice for a different climate. But... here's a question: do you let your birds out to free range? If you do so, they will destroy what ever you've planted! Pics of your set up would be helpful. If your coop/run is in a civilized yard (um... that would not be my yard!) which is not likely to be on a major predator highway, I might consider planting something that would climb on the west side to shade from afternoon sun. What ever you put as a sun block, you need to be sure it does not block the most likely paths of breezes that cross your yard, so perhaps only 1/2 of the west wall.
Plants that I've used, which have either taken over or been destroyed by the chickens: Day lilies (they really liked those) Zucchini (nice plants that provided food for all of us) Cucumbers (nice climbers, provide food for chickens.) Any of the mints, lemon balm, cat nip (that one pretty much showed up without invitation).
Peas are loved by chickens, nasturtiums, particularly the climbing ones. You could plant some cut and come again greens for the birds: kale, lettuce, chard.
Multi purpose crops (intended to be eaten by humans and chooks) I limit to those that are intended to be cooked before being eaten. In other words, if I had a lettuce crop, or cukes growing adjacent to the coop/run, I'd give those plants to the birds, but would not eat them myself due to possible contamination by air borne fecal matter. How every, I greatly enjoyed those tender zucchini planted next to the run. I washed them well, and then cooked them on the grill.
Flowers which provide enjoyable seeds: calendula, dill, nasturtium, dwarf sunflowers.
Aromatics: good for insect/rodent control, lining nest boxes: mints, citronella, lemon balm, oregano.
If you let your birds out to free range, EVER, you might consider putting a grow frame in front of your run/coop. You could plant this to white or red clover, various grasses/grains, and greens. The flock could either eat the plants that grow up through the covering wire without destroying the base of the plants, or you could harvest the plants yourself, and then feed them to the birds.
If they are always confined to coop and run, you can then have a really nice bed in front of the coop/run with plants which are more pleasing to the eye. Depends on how much effort you want to put into appearance, vs simply covering the ground.