Over the years I have experimented with different green manure crops. I like mustard but being a member of the brasica family it can promote club root. I grow giant marigolds as a companion plant during the summer. This year I harvested some marigold seed and used it for a green manure. I am so pleased with the result that I have to spread the news. The seed is easy and cheap and the crop is heavy and lush (and colourful). Has anyone else tried it? Nick.