shadecloth? plant vines against the wall? plant native adapted plants. Are you talking about vegie gardens? remember that "full sun" in most parts of the country does NOT mean "full sun" in the SW

Will they allow vines to show over the wall? A trellis with vines would be great for heat-loving vines and would cut the heat.

If not, a trellis that doesn't show, but with shade cloth to shade the wall and block the reflected heat.

Imagine the gigantic aggregate surface area of concrete block or brick garden walls for a typical city comprising maybe 130,000 dwellings with maybe 60% each having perimeter garden walls maybe 1,5 meters high. its a significant problem here in the desert southwest of the United States where night time temperatures between sunset and 3 or 4 in the morning can remain around 38C. and higher between May and October, This heat island effect along with concrete sidewalks and suburban streets designed for car convenience is killing the most drought-tolerant tree species and the iconic sajuaro cacti.

We are planting cat’s claw vines against our yard walls to drop the radiant heat to less fatal levels. Planning ordinances which require brick ir block walls to remain untouched were created by people ignorant of the radiant heat problems of brick ir block walks exposed to direct sun.