greenhouse shading

John Sowell jsowell at WESTERN.EDU
Sat Feb 13 15:29:38 EST 1999

Dear Plant Ed'ers:

We are in the process of designing a new greenhouse and working with the
architect to choose the appropriate glazing. The greenhouse will house the
teaching collection (including tropical understory/epiphytic angiosperms,
cycads, seedless vascular plants, bryophytes, lots of geraniums, and some
cacti) but will also be used for growing plants such as grasses, beans,
etc., (some of which are C4) for experiments in general botany and plant

Our current greenhouse has shaded glazing that allows transmission of about
70% of full sunlight. In addition, whitewash and shade cloth is used over
much of the collection which lowers the total transmission is about 20-30%
full sun. This has worked well because when growth of experimental plants
is required, a portion of the shade cloth is remove and the plants (even
corn) seem to do just fine with 70% of full sun.

The problem is that the new greenhouse will be in a more obvious location,
attached to the building, and it would be aesthetically desirable to lessen
the need for shade cloth. The architect has proposed using a white
translucent glazing that allows 35% to 50% (our choice) transmission of
full sunlight. This would be great for most the teaching collection but
what about the growth of experimental plants? Is etiolation a problem? Is
there anyone out there that has such a greenhouse and is now regretting it?

Thank you for your input.


John Sowell
Professor of Botany
Biology Department
Western State College
Gunnison, CO 81231
jsowell at

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