I have seen similar results with our Hairy Vetch planted as part of our N-fixer seed mix under new fruit
trees. I am pleased with the N-fixation going on as we chop and drop regularly. However, if you miss a turn, the vetch grows and smothers out anything in its pass. I like it as a cover crop on newly worked landscapes, as a means to minimize unwanted weed seeds from taking over. It can be aggressive, so make sure you want it where you plant it. My boys just harvested 1000 seed pods off the vines yesterday, so that is another ~6000 seeds to disperse over the next few months. Good stuff!