Saquaro's have flowers on top that look like birds nests or bonnets. When I went to Texas this Spring I stopped in Tucson and listened to a lecture on Rainwater Harvesting. During the lecture they showed pictures of the Tucson valley in the 1940's . It looked much like this, full of mesquite and a stream running through it. Then they showed consecutive pictures as the years went by and the trees were gradually cleared. The river disappeared. The lesson to be learned is that the trees hold the water and keep the water flowing. This is a beautiful valley in the middle of hot desert land but there are hundreds and hundreds of mesquite growing in this valley. It is green and lush with grasses as well.