Garden cloches are an attractive way to protect tender plants until they get established. You can make your own lightweight protective plant cloches using a standard two liter bottle.
If you also want to maintain humidity, just add a wine bottle cork to the top. Of course you could just use the cap that came with the bottle, but why not dress it up a bit.
This cloche pattern incorporates serrated teeth at the bottom, which allows you to work the cloche to slightly below ground level rather that just sitting on the surface. The teeth help to grip into the soil and reduce the chance that winds knock it over.