Sunday, October 26, 2008

What direction should I face my Greenhouse?

Q. In "Grow Bed Gardening," Dr. Mittleider says, "In the nothern hemisphere, face the length of the building east and west. This gives the broadside a southern exposure and all plants get the maximum light when the days are short and the sun is farthest south."

In "The Mittleider Gardening Course," he writes, "If you have a choice, orient your Grow-Boxes north to south so the shadow changes as the sun moves from east to west."

These two statements appear to be contradicting each other, in that the greenhouse is supposed to be facing one direction, while the actual garden is built with rows going the other direction. Is this right, and if so, why is the garden different than the greenhouse, and how important is this anyway?

A. Strictly speaking both statements are correct. We believe that somewhat more light gets to the plants in a greenhouse with the long side facing the sun. And in the garden we prefer rows running north and south. However, over the years Dr. M. has determined that the direction - of greenhouses and rows in the garden - are not so very important. What is important is that there be no shade, either from fences, trees, shrubs, or buildings, or from other taller plants.

Just take care of those things and then orient your greenhouse and your rows whichever way works best for you.

More often than not it's the layout of the land and the watering situation that dictates the best direction for both greenhouse and garden soil-beds or Grow-Boxes. The greenhouse needs to be level, and if changing the direction makes that primary goal much easier or less costly, then you should do it.

If there is a prevailing slope to the garden, you will want to orient your soil-beds or Grow-Boxes in such a way that the water source is at the high end, and the rows will have a fall of no more than 1" in 30'.

This often requires putting your beds or boxes rows across the slope, rather than following the slope. The extreme example of this would be a hillside, with level rows terraced into the hillside.

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