Ficus is my favorite plant material for indoor bonsai. Figs are resilient plants and are easy to grow indoors. They also show basal trunk flare, stable rootage and wonderful aerial roots suitable for many tropical and temperate bonsai styles.
What is an indoor tree?
Nature never created an "indoor" tree, so bonsai material must be able to cope with the rigors of the indoor habitat. Trees must tolerate low light, low humidity, and lack of chilling.
To be considered a good indoor bonsai a plant must be able to grow its entire life indoors, in the usual temperature range of most homes; perhaps allowing for some additional light and humidity. Ficus is a large genus of plants which contains hundreds of trees potentially suitable for indoor growth. The most commonly encountered bonsai fig is probably Ficus benjamina, the Weeping Fig, but there are many other suitable figs, and some even more suitable to bonsai cultivation.
Surprisingly there is relatively little information on growing figs indoors. More work needs to be done to determine which plants will thrive in this hostile environment. Every indoor bonsai grower is a pioneer adding to the fund of knowledge regarding plant survival and suitability. It is vital that indoor bonsai growers communicate their successes as well as their failures so the knowledge base regarding indoor materials may be enlarged. My attempt to pull information on growing Ficus indoors is compiled in my book Ficus: The Exotic Bonsai.
What makes figs suitable for indoor growing?
Figs comprise a big family of plants that can exist over large ranges of growing conditions and survive. They are naturally found in warmer climates and require no chilling period, and will tolerate great variations of soil dryness and atmospheric humidity. They are also found growing in understory conditions meaning they can tolerate relatively low light levels. Many figs have thick waxy leaves, which allow them to tolerate extremely dry air. Their natural range of tolerated conditions allows us to grow figs indoors where they encounter similarly difficult environmental conditions.
What do I need to grow Ficus indoors?
All green plants need light to survive, and more light is required for growth, flowering and fruiting. Light supplies a plant's only energy source. Growers can utilize one of several techniques to provide trees with adequate light. One, those bonsai growers fortunate to have a greenhouse usually have enough light for successful bonsai culture. Two, a south or west windowsill will provide adequate light for many fig species. Three, you can have great success growing plants under fluorescent light, if natural light is unavailable. Four, spectacular growth and flowering may be obtained with halogen or metal halide type lights.
From high school physics we may remember that light energy decreases with the square of the radius from the light source. More simply put, plants should be as close as possible to the light bulbs, as light energy drops drastically as you move the plants away from the tubes.
Fluorescent tubes are cool to the touch and plant leaves will not be damaged by close proximity to the bulb. Other types of lights will generate more heat. Metal halide lamps, in particular, burn hot so plants will not tolerate being too close to them without burning. Experiment with your light setup to determine how close you can get without burning leaves. Also remember that ventilation needs will be higher with any type of grow lamp as these all generate extra heat in your growing room.
Each metal halide lamp also requires a separate transformer box creating several other problems. Transformer boxes must be kept dry, and the transformer also emits a humming sound which can be annoying. Consider carefully the noise, and heat with metal halide lights, especially in rooms with multiple lights.
My experience in growing plants indoors has proven to me that metal halide lights installed into a greenhouse allowed my figs to be even healthier and faster growing. Since plants use light for their energy requirements the total energy they absorb is a factor of day length and light intensity. So the more hours the lights are on the more energy your plants will absorb. However, plants may require a rest period, so 24 hours of light may not be a good idea. Experiment with your light set up to determine your plants optimum day length. Remember also that some plant's key their growth or flowering as a function of day or night hours. This is not a problem with figs since their flowers are usually not significant.
Humidity is less critical than light. Most homes are incredibly dry due to the heating and cooling necessary for human comfort levels. In fact the humidity in our homes is lower than in the average desert. Any technique to humidify the area around the plants will allow better plant growth. Misting and spraying plants frequently helps but is impractical and can lead to fungal leaf and stem diseases. A humidifier close to the plants may be beneficial. Last, try surrounding the growing areas with a plastic "tent" to increase the humidity around the plants, but don't completely seal them in plastic since fungus will then become a problem.
Fortunately figs are really not too humidity dependent and will grow well in a range of humidity levels. If you are trying to develop aerial roots humidity must be maintained at high levels until the fragile young aerial roots take into the soil. Once established in the soil, humidity can be lowered to normal levels.
Temperature is a third factor in plant growth. In general most fig plants thrive indoors in a range of 60 to 100 degrees Fahrenheit. Higher or lower temperatures may result in slower growth of some plants or even their death. Figs in general are happiest with even temperatures. Avoid cold drafts especially from open windows and doors in wintertime and your figs will be happiest. If you are growing your figs outside for the summer remember to bring them back in as night temperatures get near 55 Fahrenheit to avoid subtle damage that only later may be apparent.
The most attractive feature of the figs is their gorgeous root flare and impressive trunk buttress. With this in mind, pots for figs should be shallow as this encourages figs to develop even more basal trunk flare, as well as showing them to best advantage.
In addition, figs have the very special trait of fusing their roots together with extreme ease. Therefore I hesitate to remove overlapping roots since these "melt" together over several years and help create an impressive trunk base. Overly large roots are removed or whittled down if they detract from the overall design. Do not expend energy uncrossing overlapping roots or eliminating redundant surface roots, as these too will fuse and increase the beauty of the trunk base. Even rather awkward rootage will fuse, in time, and become "fluid-looking" and more beautiful.
Basal trunk flare develops most rapidly in plants created from air layers, while cuttings are slower in developing root buttress. Certain fig species, F. palmeri, F. petiolaris and others develop a very swollen almost succulent basal trunk that can be an advantage in some bonsai. However these caudiciform figs do not branch well and thus are difficult to style as bonsai.
* Soil and Moisture
Ficus growing in pots require good drainage. Simply put, constantly wet roots mean rotting roots. Use any mix that allows for good soil aeration and even moisture content. Figs resent bone dry conditions and absolutely hate constantly soggy conditions. When figs experience these unhappy times they will lose all their leaves. Match your watering, soil mix and other growing conditions to achieve even moisture for the root system and fig growing will not be a problem.
* Leaf Reduction in figs
One of the most frequent complaints regarding figs is the large size of their leaves. Depending on the species, leaf size may vary from several feet, Ficus pseudopalma, to only an inch or two with Ficus repens nana. Fig leaves can be restrained somewhat by growing the figs under very bright light, pot culture, and with good bonsai care. Even 8 inch leaves can be reduced to two or three inches with such care.
Leaf pruning or defoliating plants in good health will result in smaller leaves when they regrow and additionally will produce back budding on many trees. Defoliation is stressful to any plant and should not be attempted unless one is deliberately working on leaf reduction and or branch ramification. Attempt leaf reduction only on very healthy plants, and those with sufficient development to require it. In tropical areas figs may be defoliated three or four times a year, but under less than ideal conditions this may prove detrimental to your fig's health.
Defoliation will also allow you to achieve back budding to fill in those "naked" areas on the trunk and branches that require new branchlets and foliage. Defoliation achieves increasing branch ramification that is superior to that achieved by simply removing all the active growing tips of the tree.
Lastly, if you wish a smaller leaf size choose a fig species or cultivar with smaller leaves which are more naturally suited to smaller and shohin sized trees. Ficus salicaria, now renamed Ficus salicaria, has small leaves useful for even small bonsai. Ficus repens nana also has vey small leaves that do not require any leaf reduction even in small sized bonsai.
Any of the usual organic and inorganic fertilizers work well for figs. Fertilize actively growing trees on a routine schedule with the recommended strength of fertilizer. When the figs stop growing, triggered by shorter day length in winter, then stop fertilizer applications.
Remember that using organic fertilizers indoors will likely result in a profusion of fungus gnats that will make you unpopular with your non-bonsai growing spouse.
Problems in growing figs indoors
Scale is probably the most common insect pest indoors. It is usually detected by seeing brown or black bumps on the fig branches. These contain an insect, which is underneath a protective waxy shell. Also evident with scale is very sticky secretions which may discolor the branches.
Mites are probably the second most common pest and are manifested by small moving pinpoints of red or brown on branch tips. Severe infestations will show "spider webs" on the branch tips and stippled yellow sickly leaves all over the tree.
Mealy bugs are yet another very common indoor pest. They look like whitish cottony areas at the leaf base and in some infestations may be present mainly on the roots and only seen during a repotting.
Use the usual chemical and biologic controls but remember that figs can show toxicity to some sprays. Dormant oil, at one tablespoon/gallon, is well tolerated on most figs while Malathion is not. Oil will not treat root mealies however and this will require a systemic poison.
Malathion is one chemical that seems to make many figs, if not all, very unhappy. Use another chemical treatment if needed.
Leaf drop in figs
Anytime a fig is unhappy it may shed all or most of its leaves. Many an anxious fig owner has panicked when their plant starts dropping leaves for no apparent reason. The most frequent cause of leaf drop is excessive wetness or dryness, but a blast of cold air or sudden exposure of the windowsill-grown fig into brighter sunlight may do the same thing. In two or three weeks, when conditions improve, new leaves will regrow, but adding another insult will probably result in the figs death. The key thing is to do nothing. Keep the fig warm and let the soil get moderately dry before watering again. If the fig has enough energy stores it will re-leaf in three or four weeks time. Should the conditions that caused it to leaf drop persist, the fig will likely die.
Virtually any of the usual styles of bonsai can be created with figs. Figs have two styles which are almost uniquely their own: the banyan style and the epiphyte style. In areas with high humidity figs can cover large areas of ground by spreading laterally. They do this by dropping small hair-like roots from the trunks or branches. These grow down until they touch the soil and then firmly anchor themselves into the ground. This transforms low branches into tree trunks that are interconnected. Photo of a Ficus salicaria (salicifolia,nerifolia, neriifolia) in the banyan style. Aerial roots are attractive and will form naturally on bonsai plants that are in high humidity, under shade, and from older wood.
Aerial roots however, will not form readily on all species of fig (Table-Ficus characteristics). Many articles have been written on encouraging figs to develop aerial roots, and most of these techniques work at times. Using a straw to protect an aerial root until it establishes itself in the ground is very successful. Another way is to graft a seedling into a likely area on the mother plant. In this one is assured of the right sized air root, positioned exactly at the proper place on the plant. Other techniques allow numerous aerial roots to begin their development, but one is never assured of their proper orientation. Once aerial roots are hardened off and growing in the ground it is easy to move them and wire them into exactly the right position for your composition.
In the epiphytic style, figs start life when birds or other animals ingest fig fruit and then deposit their droppings on a host tree. The seedling fig begins to grow as an epiphyte, using the host tree for support but never parasitizing it. Eventually the fig's roots reach to the soil and then growth overwhelms the host tree, strangles it and obliterates the original tree. "Bird-dropping" figs are found growing on buildings, bridges, brick walls or rocky hills. They can be removed from these sites, potted, and trained. One can also mimic an epiphytic style by planting several smaller figs onto a log or chunk of wood. The plants eventually envelop and fuse as they grow and form a large trunked "tree" from smaller material. On careful inspection many larger imported fig reveal that they have been created by placing several smaller figs together and allowing them to fuse into one larger trunked tree!
Which figs are best?
A very useful fig for bonsai is Ficus salicaria, the Willow Leaf Fig, also called salicifolia, nerifolia, neriifolia etc . The small leaf is in excellent scale for bonsai and the tree has good branch ramification, good basal rootage and excellent aerial root formation. If only one fig was available for bonsai use, the Willow Leaf would have to be considered. It does have the rather unfortunate habit of defoliating if stressed, so try to keep it under ideal growing conditions.
Ficus microcarpa, the Chinese banyan, and all of its cultivars, is my second favorite. It has a larger leaf than F. salicaria so small scale bonsai are difficult, but otherwise it has outstanding attributes and does not defoliate easily.
Ficus benjamina is among the less desirable figs for use as indoor bonsai. It has the habit of not taking severe reduction, and may show die-back on trunk or twigs if severely cut back. Therefore, reductions on benjamina should be gradual. Unfortunately, Ficus benjamina also defoliates rather easily when stressed.
Ficus microcarpa var. Green Island, or Rotundifolia can lose inner leaves if kept under low light and low humidity and may be less suitable for indoor growth than some of the other fig varieties.
Ficus aurea does not twig readily and so after years of cultivation it will still look sparse.
The caudiciform figs, F. palmeri, F. petiolaris and others do not branch well and so are more difficult to form into attractive bonsai.
If you desire to grow a bonsai tree indoors consider the fig. They are easy to obtain, and grow well under pot culture. Their naturally large leaves reduce well and their heavy root buttresses and aerial roots are always much admired. I know of no other material that responds as well to indoor bonsai culture.