Any greenhouse that is designed for quick and easy assembly and knock-down and re-assembly is a portable greenhouse. It just depends on what you consider quick and easy.
Some greenhouse manufacturers assure you that you can set up your greenhouse in less than 20 to 30 minutes. And some greenhouses are so lightweight and small it's simply a matter of pulling up the anchors, picking it up by the frame and moving it to the new location with a friend or two.
While you might enjoy an ideal location for greenhouse gardening during spring, summer and fall, you might be willing to sacrifice some of that horticultural excellence to bring the greenhouse closer to your house and water and electricity sources.
Or, you will use the portability to heighten daylight exposure during the fall as the sun becomes lower and daylight hours dwindle. There are collapsible portable greenhouses for about $400 for a five-by-eight foot structure that may take a bit longer for initial set-up, but then easily fold so you can move or store them for the winter.
A portable greenhouse will generally have polycarbonate or polyethylene walls and roof with aluminum framing.
To learn more about portable greenhouses, check out the shopping links at the top of this page.