I let winter take over. They didn't over winter very well. But yarrow is super rooting. Hard to kill. She still alive. I start over new cover crop seeds every year. I only trim back the companions if they compete for light. Last year had to chop all back twice. Pretty vigorous cover. I didn't notice the vetch last year. Would gave been cool to see some climbing. I dont test my soil. I just test my smoke.I know this post is from a while back. Can you give any details to how your cover crop has held up over the past year. Did some seeds over winter beter than others? Are you regularly mowing or trimming between the rows? Has the hairy vetch climbed any plants? And do you test your soil?