Article 6-1 Bonsai Grower Q’s About Lighting

I am growing Bonsai trees indoors from October to April. I have been doing this for number of years, they are under florescent tubes. They are doing okay, but not growing as well as they should. I am thinking of switching to metal halide light. The room is 10X10′. My question, should I get one 1000 watt bulb or four 250 watt bulbs?

Thank you, Peter

By switching to an HID lamp such as a metal halide, you can dramatically increase the intensity of the light available to your Bonsai specimens. I would imagine that you don’t want them to grow too quickly, as they may begin to loose their trained shape (which doesn’t come over night), so take note of the potential for increased growth rates. An HPS lamp will give you more lumens per watt of energy consumption, but the light emitted from a metal halide is often more akin to daylight. As a result, metal halide bulbs can provide closer internodal distances in some plant varieties. Metal halide lamps with 7000K ratings are often referred to as “daylight” lamps because their spectrum looks very natural to the human eye, and the increased levels of light in blue-end of the light spectrum can contribute to more compact growth patterns.

If purchasing 4-250W lighting kits the initial investment will be considerably higher than a single 1000W kit. However, you have a lot more flexibility in terms of lighting arrangements. Also, by having light originate from several points instead of one, you reduce shading and you can spread the plants out a little more as the light will overlap between lamps. Smaller wattages also run cooler so you can space them closer to the plants (possibly increasing light intensity available to the crop). They are also safer, as lower voltage levels are being discharged. If you decide to invest in multiple lighting kits in smaller wattages, consider blending metal halide and HPS lamps for optimal results.

Sincerely, Erik Biksa