Can you still cover a greenhouse the old way with straw and plastic for winter?

You can cover a greenhouse with straw and film, but this works best as a supplementary layer rather than the main protection. Straw holds heat well and creates an air cushion, while film protects against moisture and wind. The key is to combine them correctly so condensation doesn't build up inside and plants don't rot.

Usually it's done like this: first, lay straw directly on the beds and between plants in a 10-15 cm layer, then stretch film over the frame on top, but not airtight - leave gaps for ventilation or make holes. If you seal everything up tight, you'll get a greenhouse effect under the film with condensation, and everything will start to get moldy. It's better to use double or thick film so it doesn't tear under snow.

The downside of this method is that it only protects down to a certain cold - if the temperature drops sharply, film and straw alone won't be enough. If your region has harsh winters, it makes sense to add insulation material (spunbond) under the film or switch to more substantial insulation altogether. For a mild winter or to keep perennial plants through to spring, this method works pretty well.