Young iron and clay cowpeas (below) make a useful leguminous cover crop.
Buckwheat (below right) is the most manageable cover crop for hoop houses.
COURTESY NOAH SLATTERY
The hoop house is not an easy place to grow cover crops. If you have designed yours so that you can open up the ends and drive your riding tractor and implements through, you could grow cover crops. If you use a walk-behind tractor in there, you could grow the shorter, less rambunctious cover crops. If you use only hand tools, this will restrict any cover crops you consider.