The fourth graders created these awesome patterned cactus using sharpie and watercolor.  They were given a quick demonstration on how to draw different types of cactus, as well as a visual of a variety of cactus to draw from if they chose to.  We then talked about creating patterns aiming for 50% of the pattern to be black and the other 50% to be white.  Students were able to choose whatever colors they wanted to paint, but were advised to think about contrast.