I grow it. It grows really quickly with flowering beginning in a few weeks, perhaps three weeks from a late spring sowing, though longer at other times.
Insects like the flowers which is the reason I grow it, The seeds while easy to collect are not all that easy to dehull, the seed coat is hard and inedible. They don't ripen all at once.
As beersmith says the seeds are sold for green manure but once you have grown some there is no need to order more simply save some seeds for the following year.
As a green manure it is quite easy to dig in. As an insect attractor it I excellent. As a food source it is too fiddly for me
