My new Montana growing room has no skylights. Nine 1,000 watt metal halide lights are hung from the ceiling to supplement the natural window light. The plants NEVER go outdoors, even in summer, and must survive only on this light. At our location at a 5,000 foot elevation, frost is possible any day of the year. This makes the plants housebound.
The plant room floor is waterproof so careful watering is not required. A centrally located floor drain removes the overflow. Plants are all arranged on wheeled food service carts. This allows the trees to be rotated, repositioned and household chores to be done with ease despite the huge size of some of the trees.
Visitors to the plant room are impressed with the health and vigorous growth that can be achieved with artificial illumination. I'm happy to summarize and share my high-light experiences and conditions with the bonsai community.
The number one factor in growing plants is water, since plants will survive only one week without it. Light is the second most important factor and it is the "food" supply for your plants. Green chlorophyll in the leaf and stems transforms light energy, water, carbon dioxide, and minerals into sugars and everything else a plant needs to survive.
Left photo: Jerry's plant room with metal halide lights suspended from the ceiling with waterproof floor, and plant carts.
Jack Wikle of Michigan, one of my bonsai teachers, is a pioneer of growing bonsai under regular inexpensive fluorescent lights available at any hardware store. Jack grows many plant species under fluorescent supplemental illumination and his results are marvelous! (FBnews editor note: An article by Jack Wikle also appears in this issue. Go to www.fukubonsai.com/2b2a2a.html )
David Fukumoto of Fuku-Bonsai (Hawaii) has pioneered the selection and training of bonsai materials that can be grown under normal home or office lighting. The list of bonsai materials than can be grown indoors without supplemental light is very short.
CARE OF INDOOR TREES
WATER. My trees are watered once a day with reverse osmosis water. This is water that has no salts, or minerals in it, and is the equivalent of distilled or rain water. As long as your tap water is not too mineral laden it should do well for your indoor trees.
SOIL MEDIA. I use red lava crushed to about 1/8 inch size either as 100% of my soil mix or amended with an equal volume of small bark chips. Most of my indoor trees do not seem to prefer one mix or the other. Re-potting is done every two to three years for most trees.
The left photo is Ficus retusa that had been recently leaf pruned. The original stock was purchased from Fuku-Bonsai 18 years ago.
I have had this third Ficus retusa for 13 years and have grown it under metal halide lights for the last 3 years.
FERTILIZATION. With a mostly inorganic mix, fertilization is important. I fertilize every week with varying brands of half-strength houseplant fertilizer used only after thoroughly watering the trees. I do not fertilize trees that have been newly repotted or those growing weakly and I don't fertilize during slow-growth seasons.
TEMPERATURE. The temperature range in the plant room is 65 to 95 Fahrenheit, and this seems to be reasonable for most trees.
HUMIDITY It stays fairly humid and I don't try to control humidity in the plant room. I find that most trees are not particular. Plants with thin leaves dry out in extremely low humidity while those with thick, waxy leaves tolerate dry air best.
At left is a Water Jasmine (Wrightia religiosa) imported from Malaysia 10 years ago.
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 same materials merely survive without much growth.
Casuarina equisetifolia, a high-light tree, and outside the window 4 feet of snow!
Metal halides can be found in 250 to 1000 Watt sizes. Each light comes with a transformer that can handle only one bulb, and only the bulb wattage for which it is built. So if you buy a 250 watt transformer you can not 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.
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.
Bulbs lose their efficiency over a one to two year period and will need to be replaced. They are somewhat costly to purchase. In addition, some of the transformer components burned out and I have had to replace them as well.
Light supplementation of any sort is advisable for the best growth and survival of indoor bonsai. For those who cannot supplement their indoor lighting the use of low light trees is necessary. Supplementation with fluorescent light allows more plant varieties to be grown, while metal halide lights allow growing high-light requiring plants. For those who want to grow "finicky" tropicals, I strongly suggest using metal halide light supplementation!
