Follow up to last night's post

As Maryellen mentioned last night, there is an actual reason why we are tacking old greenhouse plastic to the floor of one of our greenhouses. Last year we had disease problem in that house -- bacterial canker. One of the plant experts from the University of Vermont extension office, Ann Hazelrigg, explained that bacterial canker is a soil and seed borne problem -- it most likely got into that greenhouse from some infected tomato seeds from last year. Normally, we plant tomatoes in the ground in our greenhouses, but in an effort to avoid the canker this year, we are experimenting with a container culture. Growing in a container culture means growing each plant in a pot with soil that you import into the greenhouse. So the first step for us is to lay down an impermeable barrier on the greenhouse soil that is most likely infected with the canker. We will then put big pots on top of the plastic, fill them with a growing mix, and see what happens. Obviously, importing the soil adds to the expense, but we should also see increased production from less disease, and from a warmer starting point for our tomatoes.

We aren't really breaking any new ground here. This container culture is actually how a lot of bigger tomato growers do their greenhouse tomatoes. Up in our area, Long Wind Farm grows a ton of tomatoes, and they do all their houses in a container culture. And Karl from Vermont Compost Company was invaluable in advising us on how to think about setting up a container culture on our scale.

The problem is that tomatoes are the most profitable greenhouse crop up here, but if you grow anything year after year in the same soil (at least if you grow organically), you are bound to develop some disease problems. So we will see how this works this year.

Some people may think we are a little plastic happy around here, and perhaps we are. But in this climate, you need to extend the season somehow, and greenhouse plastic is the best option to do it. Elliot Coleman, in his book Four Season Harvest, has extensive calculations showing that growing a head of lettuce in Maine under plastic in the winter only uses about one twelfth to one third of the energy required to truck it in from California, depending on how you do the math. So while plastic may not be the absolute ideal, it may be the best we have if humans want to keep living up here all year long.