I'll have to get GS to give more details later but we use a "row cover" available from seed suppliers to shade plants and to protect them from frost. They're a white gauze type of material that comes in big rolls about four feet wide. Lets the plants breathe through it and will let rain pass through too.
My mother used to let large weeds grow up in places to shade tomatoes from the sun.
My mother used to let large weeds grow up in places to shade tomatoes from the sun.