Video: Want to protect your plants from bugs and other garden pests? This is an easy DIY solution involving a few hula hoops and other inexpensive materials.
SuzelleDIY, who is (fair warning) a little kooky, shows you how to make this "hoop house". You'll need eight pieces of rebar, shade cloth, zip ties and your boxed garden bed. The hula hoops create the large frame for the cover.
Although this technically isn't a greenhouse, since it won't protect your plans when it's cold out, you might be able to substitute with plastic sheets. Or just use this to provide shade cover for your plants.