Metal halide bulb and shade

By Jerry Meislik,  Journal Contributing Editor (Whitefish, Montana)

                     I have been growing bonsai for over 30 years, and for most of those years I have grown bonsai outdoors utilizing cold tolerant or cold requiring temperate species. I also have been growing indoor/tropical bonsai under varying conditions including windowsill, greenhouse, and using artificial illumination.  I started using metal halide lamps for my indoor bonsai about 20 years ago while living in Michigan. While there are many people who grow bonsai indoors in windowsills and under artificial lights there are relatively few that use high intensity lighting. Despite having the use of a greenhouse the addition of metal halide lights to supplement the natural light resulted in increased growth and vigor of my trees! Michigan is one of those places with limited sunshine due to frequently overcast skies. Using the metal halide lights boosted the growth of my tropical plants quite significantly even in a greenhouse.

                      Since moving to Montana my new plant growing area is a conventional room with no skylights. Seven 1000 watt metal halide lights are hung from the ceiling and operate for 10 hours each day as set by a timer. These lights and the normal house external windows provide the only light that my trees ever get. The plants never go outdoors even in summer, and must survive only on this light. At our latitude and at a 5000 foot elevation frost is possible any day of the year thus making the plants permanently housebound. Visitors to my plant room are impressed with the health and vigorous growth that can be achieved with high intensity artificial illumination. Even bonsai masters from tropical areas like Taiwan are impressed with the growth possible under these high intensity lights.

Overall view of Jerry Meislik's plant room
Plants on lower shelf are low light tolerant


                     The number one factor in growing plants is water, since most plants will survive only one week or less without it.  Light is the second most important factor and it is the "energy" supply for your plants. Green chlorophyll in the leaf and stems transforms light energy, water, carbon dioxide, and minerals into everything a plant needs to survive.  Under low light conditions most plants barely survive, and they do not grow enough to allow bonsai training, fruiting or flowering. (Go to THE IMPORTANCE OF LIGHT FOR INDOOR BONSAI GROWERS)

                     Plants vary in their need for light intensity. Some require hours a day of very bright light to survive while very few will survive in relatively low light. Many species of trees will not survive indoors under typical home illumination and they gradually starve and die. The list of bonsai materials that tolerate low light and than can be grown indoors without supplemental light is very short. David Fukumoto pioneered the selection and training of bonsai materials that can be grown under normal home illumination. Dwarf schefflera and Brassaia are the best materials for indoor growers unable to supply artificial light supplementation. See for further information on techniques for success in typical home low light situations.

                     Jack Wikle of Michigan, one of my bonsai teachers, is a pioneer in growing bonsai under regular fluorescent light. Jack's indoor trees are grown under inexpensive fluorescent lights available at any hardware store and his results are marvelous. Many plant species grow beautifully under this type of supplemental illumination as Jack's trees demonstrate. See articles about Jack in the Fuku-Bonsai website:  HOW I'VE BEEN GROWING BONSAI INDOORS UNDER FLUORESCENT LIGHT   and in the "BonsaiHunk" website:  INDOOR BONSAI - AS DIFFICULT AS YOU MAKE IT.   As you can see Jack does beautiful work with plants that can get by with relatively low light intensities.

                     I have conducted experiments with Light Emitting Diode, LED, lights to see how they will compare to growing under fluorescent lights. Initial cost for LED lights is quite high but the cost to run them is relatively low compared to metal halide lights. You can see the results of 3 experiments done with LED lights here. These tests were done with previous generations of LED lights and showed the lights to be problematic in growing plants as compared to fluorescent lights.  Newer LED lights have relatively high light intensities and better spectrum and may prove to be useful for high light requiring plants. Personally I have not purchased or tested the newer more powerful LED lights. If you have experience with the new generations of LED plant grow lights please let me know at


        Two of my other bonsai friends Dustin Mann and Jerry Peters of Michigan also like growing high light intensity requiring plants such as Ficus, bougainvillea etc. Dustin has been growing his bonsai under metal halide lights for many years and convinced me to try them out for growing my tropicals.  To see Dustin's growing area.  (See article "HOW I GROW BONSAI INDOORS" by Dustin Mann on the BonsaiHunk website)

         (Photo:  Dustin Mannís basement growing area)

               They have found that they can grow these bonsai very well under metal halide lights. Jerry Peters has been using metal halide lights for 24 years and currently has six 400W and two 250W light units. (See article:  "HOW I GROW MY FIGS AND TROPICALS"  by Jerry Peters on the BonsaiHunk website)
Jerry Peter's Plant Room
One of Jerry Peter's Figs
Jerry Peter's Fig group
Jerry Peter's Bougainvillea



                      Materials that I have successfully grown indoors under metal halide lights include Ficus, Wrightia religiosa, Buttonwood, Caesalpina ferrea, Portulacaria afra, Coccoloba uvifera, Nea buxifolia, Fortunella hindsii, Bougainvillea glabra,  Carissa grandiflora, Hibiscus rosa sinensis, Psidium littorale, Phyllanthus sinensis, Pyracomeles, Sageretia theezans, Tamarindus indica as well as many others. All these plants grow, and their trunks thicken under the high light conditions and many will flower, and even set fruit!. Under low to moderate light these materials merely survive without much growth.

                   I have not had great success growing Casuarina, temperate or sub temperate species like azalea, gardenia, box, pyracantha - probably temperature related to lack of cooling and not light intensity. I also have not done well with needled trees such as pines, junipers.



                     Metal halide lights provide high light output. The lights come in many sizes, shape and types. Another type of high intensity light is sodium. Sodium lamps are yellow/orange in color and give the plants a peculiar appearance. The sodium bulbs also allow stem elongation, or etiolation which is not desirable in bonsai but the frequency spectrum does help in flowering/fruiting.

                     Metal halides can be found in 250 to 1000 Watt sizes. Each light comes with a transformer that can normally handle only one bulb, and only the bulb wattage for which it is built. There are some newer lights that can take different bulbs.  So if you buy a 250 watt transformer you cannot later upgrade it to a 1000 watt bulb for instance. Buy the size light that you will need, as upgrading to a higher wattage bulb is not possible. Some light fixtures will allow switching form sodium to metal halide bulbs at different stages of the growth process to encourage blooms vs. vegetative growth.

                      Using metal halide bulbs you can grow many high light materials. These plants will actually grow significantly and increase their girth and leaf density. Under moderate to low light situations these plants will be almost static and not show any real increase in their size or ramification.



          These lights have the problem of producing significant heat from the bulbs. This means that the tops of the trees cannot be placed closer to the bulbs than two feet or the closest leaves will burn. The heat released from the bulbs and transformer can also make your growing room uncomfortably warm without additional ventilation.

           In addition each bulb requires its own transformer and these produce an annoying humming sound. One transformer is generally required for each bulb. Transformer noise can be troublesome in a quiet home situation. My transformers are all located in a room below the plant room for this reason.  The bulbs and the transformer must not get wet. A wet bulb may shatter so keep moisture off the bulbs as well as the transformer box. Bulbs lose their efficiency over a one to two year period and will need to be replaced, and they can be costly to purchase.  In addition, some of the transformer components burn out and I have had to replace a few over the last few years.

             (Photo:  Transformers, one for each bulb)


                     Light energy drops off greatly with distance from the bulbs. Higher light requiring plants are placed on the top shelves. Low light plants can be placed on the lower plant shelves, farther from the lights. Even low light plants grow better and develop faster when closer to the light source.  Many of my Scheffleras and Brassaia are kept on the lower shelves as top shelf space is so limited in my plant room.

                     Look at the table below to see how light falls off drastically as distance from the bulbs increases. Light fall off varies as the square of the distance. So at 1 foot the light energy is one unit but at two feet the light energy is .25 unit!!   From the table below you can see that sunlight provides a huge amount of light energy, even a position in a west window provides a huge amount of light energy.

                     Metal halides are relatively weak compared to sunlight or even a window in direct sun. Strong growth is possible in windows with several hours of south or west exposure. Rotation of the plants will be necessary to expose all sides of the tree to the light.


Foot Candles or Lumens


Sun Outdoors 5-7-2013



West window sunlight



3' from metal halide(MH) light



Shade Outdoors 5-7-2013



5' from MH light



Lower shelf with plants



West window shade



Dining room 5' under incandescent




                     Light supplementation of any sort is advisable for the best growth of indoor bonsai. Those who cannot supplement their indoor lighting must use low light trees. True Indoor Bonsai will do well even in normal bright room lighting.

                     Supplementation with fluorescent light allows more plant varieties to be grown, while metal halide lights allow us to grow many moderate to high light requiring plants. For those who desire to really grow those "finicky" tropicals I would strongly suggest using metal halide supplementation.

                     - - - Jerry "BonsaiHunk" Meislik   (



                     I thank Journal Contributing Editor Jerry Meislik for a fine informative article and for introducing his Michigan friends.  I had the pleasure of visiting Jack Wickle's home and was very impressed with his carefully tending miniature bonsai.  Now I am impressed with Dustin Mann and Jerry Peters who also use metal halide lamps. Jerry will have additional exciting Michigan bonsai news in next month's Journal. 

                     Most know Fuku-Bonsai for our work with the lowest light tolerant Dwarf Schefflera and although these do well with the spill-over or lower light,  their growth improves with as much light as possible and when properly acclimated, watered, and fertilized, they will grow in full sun provided night temperatures are above 55įF at night.  The Journal of Tropical and True Indoor Bonsai was created to include tropicals that need more light than Dwarf Schefflera and we welcome those growing such tropicals outdoors in warmer climates and indoors under lights in cooler climates.   As you can see from Jerry's chart above,  there's a lot of light in windows that get direct sunlight.  While it may not be enough for high-light tropicals,  Dwarf Schefflera will absolutely thrive, especially with humidity trays!

                     We've come a very long way from the days that bonsai were only outdoors!  Your success will largely be based upon your selection of plants,  the quality and potential of your starter material, AND HOW WELL THE PLANT WILL GROW FOR YOU IN YOUR ENVIRONMENT!  We hope these Journal articles help you to improve your growing conditions, increase your bonsai success,  and for your bonsai to bring joy!

***  Return to June 2013 Journal of Tropical & True Indoor Bonsai
***  Go to Mid-Pacific Bonsai Foundation website
***  Go to Fuku-Bonsai website
***  Go to Jerry Meislik's website
        © Mid-Pacific Bonsai Foundation, Fuku-Bonsai, Jerry Meislik, 2013