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This is a Sand Spur. A type of grass that has very sharp, painful burrs. In spite of that, most of the plants that you see (and step on) have been planted by people. Why?

Answer:

While they are not planted intentionally, a vast number of them are planted by people. The next time you see sand spurs, notice where they grow. They will be very thick along pathways.

Why? You walk along the path and "Ouch!" You step on one of these spiny plants. You manage to pull it out, while sticking your fingers a few times, and then what do you do? You throw it on the ground! Where it grows into a new sand spur. You have just done exactly what the plant wanted you to do.