|The Winter Harvest Handbook, by Eliot Coleman|
This book talks about growing winter-hardy vegetables in an unheated greenhouse in Maine, which is considerably colder than Western Washington in the winter, and it covers a variety of topics.
I think this book is aimed at people who want to have market gardens or to increase their utilitization of their land during non-typical seasons. The basic technique espoused is to have a hoophouse which provides some cover, and an inner crop-cover, which provides further protection.
The author describes situations where the outside temperature is very low -- 10 degrees F or -12c, where the inside temperature at soil level is in the low 40s or high 30s. That's enough protection that cold-hardy vegetables will not be affected, and allows cropping of fresh vegetables during winter.
What is of particular value, if you're considering doing this for a market-garden application, is the discussion of planting schedules and seccession planting. You plant the winter vegetables in the late summer or early fall, in waves. The maturation is slower than it would be in summer, but the spoilage is, too. So your salad greens have a longer harvest period.
He talks about moveable greenhouses, mounted on skids, on specific types of vegetables that grow and sell well, and has useful notes on marketing vegetables and establishing a brand that consumers can follow.
In my temperate marine climate, where the average high temperature in January is 47 degrees F or 8 degrees C and the low is 36 degrees, or 2C, I'm curious what temperatures I could achieve in an unheated greenhouse. 47 degrees is only 20 degrees from tomato temperature. Hmmm...
The compost that I produce throws off a lot of heat as it converts. I wonder if I couldn't get to tomato temperatures by using a hoophouse on a few feet of compost.
There are tables and planting schedules for their farm, as well as the general layout and the size of various fields and structures. It also has pictures of the packaging and talks a bit about what sells and what doesn't. That sort of information is hard to come by.
Finally the book talks about tools and jigs to make planting easier, and I found that discussion to be pretty useful.
For anyone considering building a hoophouse I'd say this is a useful book, and it certainly has made my seed-catalog perusing more interesting.