it probably depends on where you are. this will be my 3rd year with it. it did reseed last year, but i had pigeon problems. my season is relatively short, so it did not reseed and grow again in one season. i believe i have solved the bird problem, so i hope that there will be more from last years crop that will grow on it's own. cindi said hers did spread. i planted over an acre and there is plenty more room, so it can spread as it wants.
it does not seem to compete well with pasture grass. i had to plow up each year the area i have planted. the bees really liked it and i got some of my late season honey from it.