Greenhouse Science: Corn + wood = onions

Tucked into the large greenhouse and tunnel complex on the east side of Intervale Road you’ll find a single heated greenhouse where we start all of the seeds we’ll transplant to the fields when the ground warms up. It’s important to know this greenhouse is the only one we heat.

Of course you’d expect we’d have to have a warm place to start seeds given Vermont weather! We can go from 5 inches of snow to 47 degrees in a day, as we did last week, so imagine the variables we face when opening the greenhouse the first week of March.

We use a combination of heating fuels for the house. Several years ago we installed a biofuel furnace to reduce our dependence on propane. At this time of year, Jill fills the fuel hopper with about 200 lbs of a mix of wood pellets and dried corn ( 1:2 ratio.) At night the propane will come on as needed to achieve our desired temperatures.

The daytime temperature goal is 72 degrees. The louvers open at that point and then the vent fan turns on at 76 to keep the temperature steady. The overnight temperature goal is 60 degrees. As the nighttime temperatures rise we’ll use less biofuel and propane, as you’d expect, because the sun helps with the warmth and the double layer of heavy plastic traps a cushion of warm air .

Over the course of the heating season, we usually go through 3 tons of wood pellets and 4 tons of dried corn.

Our efforts pay off when the first onions come up!