Indoor Plant Lighting

Thomas Bjorkman Thomas_Bjorkman at
Thu Jul 14 09:17:41 EST 1994

In article <301bne$a2s at>, njj at (Neil Johnson) wrote:

> High Pressure sodium are now considered the #1 best all around hobby
> grow light (with metal halide a close second place). In almost all
> cases a single 400W HPS will beat the results of a 400W MH. In
> addition 2 400W HPS will out perform a combo of 1 400W HPS & MH each.
> The High Pressure sodium is available in a color improved version
> called Son Agro (Philips?). This version has more blue.

In our greenhouses we have tried both MH and HPS for supplemental lighting
in the winter.  (These are 1000W bulbs in 22" luminaires).  With beans and
cole crops the growth under HPS has been unacceptable, whereas MH prodcues
great plants.  I suspect the sensitivity to the spectral variation will be
rather species specific.  TFor instance, the cole crops are perfectly happy
in growth chambers with only CW fluorescent.  Try that with radishes and
they will commit suicide through excessive hypocotyl elongation.
Thomas Bjorkman    Dept. of Horticultural Sciences   Cornell University

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