I don't think it would be necessary. I'm currently starting one myself. I've focused on things that cold hardy in my zone along with dynamic accumulators like comfrey. Some nitrogen fixers like clover and black eyed peas seem to help.
I have a 20m by 20 meter (60ft by 60ft) plot of land, everyone has a free range cow should I have one too, I am also allergic to milk and dont like red meat.
If I remember correctly your minimum winter temperature is above 50F (10C). So a greenhouse would not really protect your crops from the cold.
A greenhouse will trap heat and make your plants melt in the summer. I remember you stating that you have to "pipe" water in because you dont get alot of rainfall.
So short answer I dont think that it serves any purpose in your location. If you can list 5 reason why you think it might be a good fit and another 5 reason why it is not. Then I can give you my opinion based on that.
Location: Wellington, New Zealand. Temperate, coastal, sandy, windy,
posted 5 years ago
Ronaldo Montoya wrote:... necessary to have a green house in the forest garden(...)or can i avoid this?
As the other posters said-I can't imagine it would be necessary, or even desirable in your warm, dry climate.
On that subject, people can give much better help if the poster has some climate info and general location on their profile
The perennial plants I start need to be able to cope outside;
the only things that get extra warmth are subtropical annuals like eggplants-but my climate's not in the least tropical
Ronaldo, I'm interested to know whether the info your reading is talking about climates like your own?
I don't think of greenhouses as being designed for tropical climates, only temperate or cooler.
Something that I imagine could be very useful in your climate is a shade house, which protects plants that have evolved to begin life in a forest understory