Most gardeners and farmers talk about weeds as though they are an anathema. Once upon a time, I was one of them. I spent lots of hours trying to eliminate every weed. Not any more. I now don't mind if some weeds co-exist in the gardens as long as they don't over proliferate. And I now see weeds as a resource to be utilized. Not that I want my gardens to be so weedy that it deminishes my harvests, but weeds can at times be beneficial.
Certain weeds can be used as catch crops for pests. I notice that whitefly seems to infest the volunteer nasturtiums before invading the rest of the garden. Thus I can aggressively treat the nasturtiums without jeopardizing my edible crops.
Some weeds are liked by the rabbits and chickens and make a nice addition to their diet. In fact, I now intentionally grow purslane, elevating it from it's weed status to a fodder crop.
Most weeds, except the Bermuda grass, can be cut off at the soil level and controlled, acting as mulch. I will pull & drop, or chop & drop, weeds all the time. Why bother carrying them to a compost pile if I don't need the fill? Just leave it where it drops and let it become mulch.
I use some shade loving plants to grow in areas that I can't use for most vegetables, like in the photo above. They are weeds, but I use them as a resource. They grow where little else will. I harvest their leaves to use as mulch and compost. They grow back without any assistance in my part, so I can re-harvest them again in the future. Pictured above, a type of philodendron grows under the coffee trees. A type of fern also grows there. Eventually they get prolific enough that I can quickly harvest trashcanfuls.
It doesn't take long to clear under the trees. I used these leaves and stems as fill for a pallet grow box. And even though the ground looked clear after pulling, I know from experience that the plants will grow back again. So you could say that thus area has given me a harvestable crop -- weeds.
Weeds also help trap fallen leaves that would otherwise be blown away in the tradewinds. In areas without weeds, the ground tends to be bare. With weeds, the ground gets coated in a natural leafy mulch.
One other thing that I've noticed about allowing weeds to grow and be harvested in my shade areas. The soil there has a much better look to it. I don't know why. But the soil looks better than in shaded areas with no weeds and those shade areas where I don't harvest the weeds. I guess there is something going on with the weed regrowth process and soil health. So totally excluding weeds doesn't seem to help the soil, nor does allowing weeds to totally fill in and maintain a status quo. There is something to the repeative partial clearing. I don't understand the science behind it.
I've also taken advantage of weeds to help establish my pastures. A friend was eliminating weeds from her landscape gardens, including among them a viney weed that livestock love to eat. The weeds were heavy with seed. So I brought the bags and bags of weeds to my pasture areas, allowed the weeds to dry out, them carried them around the pastures giving them a good shake to scatter the seeds. Many of those seeds are germinating, helping to fill in bare spots in the pastures with edible weeds. The sheep will appreciate it.