Posted: 05/11/2017 at 07:19
Most of those will withstand quite a bit of frost so I'd follow Obelixx's suggestion. Put the small pots together into a bigger pot or similar, and tuck them somewhere against a house wall. You can add a bit of fleece or polystyrene round them during prolonged periods of frost. The plastic greenhouses will protect against wet and wind, but don't offer much insulation.
I leave small pots of perennials out all year, tucked against the house wall, or in among evergreen shrubs in the borders. They withstand pretty much everything my climate here chucks at them. We've already had several frosts in the last few weeks, and even the tiny ones I've grown from seed this year are fine that way.