Ask Mr. Smarty Plants

We're assuming that when you say "white" you actually mean "translucent." We made a field trip to the Lady Bird Johnson Wildflower Center to ask some of the experts on the staff about the answer to this question, and to look at the greenhouses on-site there. Of course, the greenhouses there are the large commercial type greenhouse, and there are several styles. The main Nursery greenhouses have clear glass side panels and a translucent corrugated PVC roof. They also have shade screens that can be opened or retracted to control the amount of sun. In the summer, of course, the greenhouses get very hot and even the open, unroofed plant beds have shade screens over them. The greenhouse functions to protect seedlings or tender plants being wintered over from the cold, but it also can be useful in the summer, provided arrangments are made to keep the plants (and the gardener) from frying.

Since construction is a little out of our area of expertise in native plants of North America, take a look at this Greenhouse Construction website, which has other links that might be helpful. Another useful site is Hobby Greenhouse Construction, which touches on the many different materials you might wish to use.

Because you are building your greenhouse in the same area as the Wildflower Center, you will be interested to know that the consensus seemed to be for translucent PVC panels with some sort of shade screen available. In Central Texas, you will be protecting your plants from extreme cold only a few weeks a year and from extreme heat most of the rest of the time, and need to keep that in mind when you are selecting design and materials.