Orchid Lighting

by Thom
(Pittsburgh)

Could you give me an idea how much heat a 175w metal halide fixture would give off? I saw your page about airflow and how the self contained ballast units (like some Sunfarm units) are the worst to cool.

I have only a few orchids in a 2x2 ft area. I'm thinking T5's or cheepy fluorescents might make better sense than the much pricier and hotter MH system. Thanks again for your advice and input!

Answer: Thom- Just to give you an idea, a 175 watt Metal Halide turned on inside a 2x2 enclosed space will bring it up to 105 degrees in about 15 minutes.

Plants like orchids do not need quite as much light as tomatoes and peppers (for example), but still require a fairly strong light source to bloom at their full potential. T5 lights are very well suited for orchids in this way. Plus, as you guessed, they put out half as much heat....making them easier to manage in the Summer.

As long as the growing space for your orchids exchanges air freely with a much larger air space, the heat from a MH light will not be too difficult to control. However, many orchid growers use smaller enclosures to help keep the humidity up (or to manipulate the photo period and force blooming). The smaller the enclosure, the more of a problem this excess heat becomes. Even if you are growing your orchids in a large, open room, the heat from a Metal Halide may still be enough to make things uncomfortable in the Summer.

Last but not least, you could use regular 4 foot fluorescent shop light fixtures. Two of them, side by side, kept three inches above the tops of the plants, would be sufficient as long as you are growing a variety that does not exceed 14 or 15 inches in height. Just be sure to purchase the fluorescent bulbs with the highest lumens....this is a measure of usable light as far as the plants are concerned. This would by far be the least expensive effective solution. I have seen these fixtures for as little as $10 a piece at Lowes or Home Depot. Plus, they put off very little heat.

I hope this helps you out Thom, and Happy Growing!