Fockea edulis -- young plant

Winter Care of Tropical and Subtropical Bonsai

Hardy - Sub tropicals - Tropicals.  Why exotics?  

Tropical: 60-90 F, 12 h daylight throughout the year. Plants are not programmed for a rest period, but it is possible to slow their growth. To keep them going full steam would take a lot of investment and high energy use.  Representatives: Ficus, Serissa, Shefflera, Carmona. Succulents like Portulacaria.

In my P.T. area, the biggest winter problem for my tropicals is light: short gray days. My greenhouse solution (October-April): see Picture. Wall-mounted shelf system with hung "Shop Light" fluorescent fixtures, double four foot 40 W fluorescent tubes, 240 W total. Twelve hours per day. Distance of plants to the light source. Functions of light: it drives photosynthesis and inhibits growth. Bending towards the light. Amount of light provided is only 5-10% of outdoor summer light. On the rare sunny days, my lights are turned off.  

In Richards talk on "Bonsai and light" he mentioned much more but my memory is not what it once was. I do remember the following however.
" Light intensity decreases with the square of the distance from the source. In other words, if a plant one foot away from the lamp receives 100 lumens, the one two feet away receives not 50 but only 25."

Temperature Thermostatic space heater. During Dec.-Feb., plastic foil enclosure of "tropical" area (55-65 F). The rest of the greenhouse only receives "leaked" heat, 40-55F; OK for sub-tropicals. Moderate energy use. Other care: reduced watering, no fertilizer in mid-winter, moderate training and pruning only.

Examples: Big F. benjamina (10 yr.) from small cutting (1-2 yr.) Grove: 2004 demo. Branch problem by 2007. P. Adams advice. No new branches. Extreme weeping solution.
Unhappy Willowleaf Ficus. Defoliation is not desirable, but not fatal either. Reduce water further during the defoliated state.  Succulent Elephant Bush (2005 cutting); extreme water deprivation in winter avoids leggy growth. 

Subtropical: Rest period in winter, but not total. Protect from freezing, but low temperatures around 35-50 F acceptable. I keep Citrus and Orchid cactus in the low-heat portion of my greenhouse. Other sub tropicals like Olive Japanese holly, Ice plant, I shuttle in and out of my unheated garage. Temporary shelves under high garage windows. Dolly for large Grapefruit. Rolling bonsai table, wheels & rim.

This was written in an outline form for a presentation to our Bonsai club.  Plants listed were shown.  I think it still offers good advice, even when written in a telegrphical style for a talk.

 (c) Richard Bartha