Portable Greenhouses better than permanent greenhouse
So you can't afford the expense of building a permanent greenhouse - what are the alternatives? Well, there are more and more portable greenhouses coming onto the market, and these have the distinct advantage of being able to be erected not only wherever you want, but in a very short time - there are even several models measuring anything up to 8ft x 8ft which are self-erecting! Most models of the conventional oblong shape are in the 6ft to 10ft range, though there is a range of dome shaped portables with diameters going up to over 20ft.
Most larger portable greenhouses have a frame constructed out of powder coated steel - notable exceptions to this are the large dome shaped structures which have an external frame of pvc piping from which panels of woven translucent material are suspended. The self erecting greenhouses operate in the same way as self erecting tents. Smaller models can even be placed on your patio, though wherever it is erected much thought must be given to the possibility of strong wind conditions. The structures are quite light, and must be well anchored so as to be prepared for such conditions.
Unlikely to be needed for the entire year round, the portable greenhouse can be erected and ready for use in early Spring, enabling you to propagate seedlings in a warm, humid environment so that you get mature plants several weeks before you normally would. The greenhouse may be taken down and stored during the winter months and re-erected the following Spring. Models normally weigh between 20 and 40lbs.
In the most part, portable greenhouse do not come with any propagation shelving, and when budgeting allowance should be made for any shelving that you need to use. The greenhouses are, generally speaking, sturdy and the coverings UV protected and rip-proof. There are normally one or two doorways and several vents, depending on the size of the model. Doorways and vents are zippered and most models have a place for the attachment of a hosepipe and electric cable. Most greenhouses come with several anchor points, though anchors and rope are sometimes an optional extra.
It is, of course, possible for you to design and build your own portable greenhouse using pvc electrical conduit and its end joints. These can be bent and fixed into a Nissan hut shaped structure - that is the shape of a half cylinder of semicircular cross section. This structure can be fitted with a convenient plastic cover, anchored at the sides or covered with earth. The structure needs to be attached to stakes at its four corners to ensure protection against strong winds.