We have always allowed weeds to grow in the middle of our orchard rows, mowing them to keep them under control. I like that it keeps our soil cooler, and prefer to work with what we have rather than against it. I’ve seen and number of instances where a low weed cover will lower soil temps at 2″ deep around 20 degrees F (from 105 to 85 would be a fair average). Weeds do not provide the benefit of a cover crops, though, because the plants are designed to efficiently reproduce and put little energy into roots or biomass, but rather into reproduction. We have started using cover crop mixes instead, but like most folks haven’t found a good mix that gives us everything we need., as the decisions are more location based than universal. I hope that helps.