Expert: Sarracenia Northwest - 9/18/2011

Question
I just puchased a 1000 watt metal halide for my small 8x6 greenhouse and I had a couple concerns is that going to get to hot or too much light most of my plants are from you two and dont want to do somthing stupid.I read that  you were putting some 400 watt halides in your greenhouse so I thought it would be a good idea for me too do the same heat and light all in one!Thanks Jacob and Jeff for taking the time to help me out any info. would be great.P.S Is any bulb O.K. to use?

Answer
Your bulb will generate lots of UV light and get very hot.  To avoid burning your plants with the extra UV and heat, you'll need to place them at least 5-6 feet away from the bulb.  Given the size of your greenhouse, the 1000-watt bulb might be too large.  In fact, you might be better off with one or two 400-watt bulbs placed strategically so that you have even distribution throughout the greenhouse.  We're using 3 400-watt fixtures placed in a manner to give certain plants optimal lighting.  This type of setup is ideal when height is limited.  The 1000-watt bulb is best used for much taller and larger greenhouses.  

If you choose to stick with the 1000-watt bulb, I strongly recommend installing a moving track to move the fixture from one end of the greenhouse to the other.  This will limit the amount of overall exposure and reduce the risk of plant burn.  We use a single 1000-watt bulb in our sundew greenhouse, and we have it set on tracks, traveling about 8 feet every minute or so.  

The other concern is the type of fixture you're using.  Typically you see this type of fixture in workshops and such.  It's not rated for damp areas, such as a Nepenthes greenhouse where you would water liberally and allow the water to drain through.  You'll need to be extremely careful about getting any water splash on it while the lights are on.  If water hits the bulb while its on, the bulb may explode.  With this in mind, you might need to water your plants when the light is off.  

Here's a site where you could learn more about metal halide lights.
http://homeharvest.com/SunburstCompactConvertible.htm

Look for an upcoming podcast on this topic.

Good growing!
Jacob Farin