This plant starting growing next to my porch and I have never seen anything like it. Each stem has exactly 6 leaves that are open to the sun. At dusk the leaves begin to collapse in on each other and by dark they are completely closed against each other, pointing at the ground. I don't know if I should pull it up, replant it, or let it alone. Please help identify it....
There is a relative that is native to N. America: http://www.botanicalgarden.ubc.ca/potd/2007/07/senna_hebecarpa_1.php