RE: Inquiry regarding P2 for greenhouse managers

[herrick@admin.njit.edu]

The challenge to operating a greenhouse is keeping a glass structure warm 
in the winter and in the summer providing as much light as possible without 
cooking the plants.  Even in winter, the sun usually warms up the greenhouse 
during the day.  One can buy space blankets that roll out at night to create 
a ceiling that reflects heat back down to the plants.  For both summer and 
winter, the glazing below the level of the benchtops is wasted.  Consider a 
solid wall with earth banked up against it for insulation.  Also consider a 
geothermal fresh air supply.  In the summer most greenhouses operate large 
fans to exhaust the greenhouse-heated air.  Obviously, the air is hottest at 
the top, so venting at the ridgeline is effective.  The greenhouse industry 
also slathers a white coating onto the glass when the sun is too intense for 
the plants.  Shade cloth is also available.  As much as I try not to miss an 
opportunity to plant trees, greenhouse shading is probably not the best reason 
to plant trees.  The more sun the better as far as photosynthesis is concerned.
Even a tree with a lacey canopy such as honey locust would cast too much shade 
if yuo could manage to locate it wher it would provide any shade at all, and in the winter the branch shadows would steal a surprising percentage of the light.

It has been years since I actually worked in a greenhouse, so I'm afraid I'll 
have to let you search out the details (brand names, suppliers) yourself.  

Your county extension agent would be a good place to start.

There are, no doubt, P2 opportunities with the pesticides used in greenhouse 
management.  Integrated Pest Management (IPM) should yield immediate savings.  
In addition, there are lots of options to consider: disease resistant varieties,
scrupulous cleanliness, etc.  Again, talk to your extension agent.  Good luck.

Bruce R. Herrick, Ph.D.
NJIT