Post by astrid on Nov 16, 2015 17:23:23 GMT -6
I have had a greenhouse on the bc coast, zone 8/9, for the last few years, and some things I have learned have been surprising. The most surprising thing has been that the season is not extended as much as you might expect. The main reason for that is lack of light. When it is cold outside, the days are short, so plants don't grow well unless you have power and grow lights to supplement the daylight. You can mitigate this by getting things started inside the house but only if you have broad spectrum bright lights inside (ie electricity). This effect is particularly noticeable if your greenhouse is plastic covered, which many are because it is much much more affordable. Plastic blocks out 10%or more light, making early and late season growth more difficult. If you can put pre started plants in the greenhouse about the same time you can plant seeds outdoors, you will be way ahead, but that does require lights from somewhere to get the plants well started. Established plants will keep going in a greenhouse for longer than outside, and things like new Zealand spinach will survive over winter and get going again early next spring. But, you need a really large greenhouse to grow a variety, and without power the advantage is not what you might think.
Glass greenhouses are great, but in warm climates they can easily burn plants, growing season is short on either side of summer unless shadecloth and big vents are used. It takes lots of reading and experience to get it really right. My friends think I have a green thumb, but I am glad I am not trying to live entirely off of what I grow. I would starve, no two ways about it.
Also, in post volcano scenarios, IMO a greenhouse would make very little difference unless there was power to supply lots of light.