>>386073Don't forget crop rotation so that pests that overwinter in the soil for 1 type of crops won't have the advantage of having lunch as soon as they hatch, if you plant the same types right over them again.
If you really want to take it to the next level, turn all those into raised beds, using blocks, that you can also attach polytunnels to. Just the raised beds alone can extend the season on both ends a good bit and covering with a polytunnel will do even better. As it gets colder you can add a second layer of plastic.
To really help out during cold snaps and to extend the season you can add thermal mass to the polytunnels in the form of containers of water. Sanding and painting the container black will help them convert sunlight into thermal energy so it can be released more easily at night. This will help prevent fast temperature changes. You can use any size container from 16oz soda bottles to 2 liter soda bottles to 55 gallon water drums. Just don't use regular milk jugs for very long because HDPE plastic is easily destroyed by the sun and forms cracks on pressure points. Soda bottles last for many years. Smaller bottles and containers are easier to place in and around plants. Any sections you let go fallow can be stacked with thermal mass that can help the rest of the polytunnel.
Even without polytunnels, adding thermal mass to the area will help extend nighttime temperatures and hold off frost longer. One polytunnel can cover a couple rows too. Just make sure there's proper ventilation, during the daytime, or things can really over heat if the weather isn't really cold during the daytime.
Skip to 11:27
http://www.youtube.com/watch?v=ovR-OZlul3w#t=687 