There are steel greenhouses as well as plastic, aluminium and wood. My recommendation would be for one of the latter two, they are both excellent but each one have different merits. I find the wooden ones, particularly if made from cedar wood, to have a very warm feel about them whilst the aluminium types will never need any maintenance on them.
Growing Parsnips
25th July 2007 I am often asked what is the best method of growing both long carrots and parsnips for the show