At the little farm where Joe and I volunteer on Saturday mornings, the lower field has so many rows of greens - mustards, collards, radishes, and a little bit of kale - that there is no way for us to fully harvest the crop.
The guys who manage the farm, who pay attention to the farming lore of local old-timers, plant the field each fall from end-to-end knowing full well that many perfectly good greens will go uneaten, just like in years past. For them, even though they enjoy eating greens, the main point of that crop is not so much Food as it is Pest Control.
They call those greens their "fumigant crop", and it is planted to keep the root-knot nematodes at bay. In spring, when they are ready to plant the warm-weather crops, they just turn under all the remaining greens to let them finish their good work of pest-control. Not too surprisingly, research supports the practice of the old-timers.
The book Managing Cover Crops Profitably, published by SARE (3rd edition, 2010), which can be downloaded for FREE, cites research that demonstrates the "nematicidal effects" of Brassica-family plants like mustard greens and radishes.
When I was talking with a county resident last week about his garden, he mentioned that he'd been having trouble with root-knot nematodes in his 1.5 acre garden over the past couple of years. I told him about my friends and their field of greens, and he went silent for a minute. Then he said that he hadn't planted greens as a winter crop for the past few years because his freezer was full, but he had in each of the previous 20 or so years of gardening in that spot.
I am pretty sure that, regardless of the state of his freezer, next September my new gardening friend will be planting a whole lot of greens.