Thanks for the kind comment! We have done a little bit with low tunnels in the past, but they have somewhat limited usefulness. (Mostly for small plants, only in the shoulder season.) We are retrofitting our raised beds with hoops this year, but it’s mostly for remay/frost cloth to deal with an onion maggot infestation we got last year. We may also outfit those hoops with a plastic cover for early/late season extension at some point. As for perennial veggies, it’s tough but there are a few! Chives, asparagus, rhubarb and horseradish are all hardy to zone 2/3. Sorrel is zone 4. Some mints are supposedly good to zone 3, but we’ve struggled to find one that survives. At some point, we want to look at using cold frames to try some zone 4/5 perennials. This technique works great at lower latitudes, but we don’t yet have any insight into subarctic performance. Hopefully that helps!