You grow broccoli rabe like any other plant in the cabbage family. If it is going to seed too quickly it is probably in an area that is too hot and dry. These plants like cooler temps of spring and fall. Try again in the fall and pick a place that does not get so much direct sun all day. Not a shaded spot but a place where the sun fades the quickest. I have a spot in my garden that gets direct morning sun but tless afternoon sun. My cabbage family lasts the longest here.