DEPENDS ON how much shade you want. sounds like it should work to me. but the blue tarp will not last as long as long lasting shade cloth. the sun will break down the blue tarp sooner than good shade cloth.

let us know how it works out.

The difference between a blue tarp (or any other kind of tarp)and shade cloth is that tarps are solid. Shade cloths are woven so that the as the hot air rises it escapes through the porous weave. The point of shade cloth is to cool down the soil, not only by keeping the sun from hitting the plants and ground, but also elimate heat build up. Go with the shade cloth if you are thinking about cooling down the lettuce patch and extending the season.