Care SheetsTemperate Bonsai Care Sheet
These are general care guidelines for temperate bonsai. Some of the more common temperate Bonsai trees include Chinese Elm (Ulmus parvifolia) cvs.; Cypress ''Andelyensis'', obtusa gracilis, obtusa gracilis nana, pisifera nana, ''Tskumo''; Heavenly Bamboo (Nandina domestica); Juniper procumbens nana; Juniper sargentii ''Shimpaku''; Myrtle (Myrtus communis); Olive (Olea sp.); Pomegranate (Punica granatum) cvs.; Rosemary (Rosmarinus officinalis) cvs.; Thyme (Thymus vulgaris).
Placement and Temperature
Temperate bonsai are trees that are native to climates which have four seasons. In addition to proper watering technique, temperate trees need to feel the change of the seasons. The best way is to keep them outdoors in light to moderate shade when night temperatures are above 28-30F. In Maine this usually occurs from late April until early November. If your tree will be grown indoors a bright east window is best, north second best. Southern or western exposures can cause the soil to dry out very quickly during the heat of summer.
During the winter months temperate bonsai should be kept in a spot with the night temperature between 28F and 55F for a minimum of 2 to 3 months. This will provide a dormant, or rest, period that all temperate plants require. If the temperature is always below 45F the trees will remain fully dormant and will not require light during the dormant period. An unheated basement, a root cellar or a refrigerator are good spots which will provide a constant, cool temperature. If your winter spot is between 45F and 55F at night, the trees will continue growing slowly and require light. An unheated or cool room or an unheated sunroom are good spots. Avoid drafty or open windows since they cannot provide a cool, even temperature.
Remember that temperate bonsai need to feel the change of seasons and try to duplicate this seasonal change in temperature. The more closely the native climate of the tree is duplicated, the more your tree will thank you with healthy growth and a happy appearance. See the Basics of Bonsai pt 1 and pt 2 for more on this.
Misting and Humidity
If temperate bonsai are kept indoors during the cold part of the year, they should be misted daily to compensate for the low humidity in homes. For proper temperatures and suggested locations, see Placement and Temperature. This is particularly important during the winter heating season. Avoid placing any bonsai near a wood stove or a hot air heating duct since no amount of misting will compensate for a constant blast of hot, dry air. Also avoid placing bonsai on top of electronic appliances such as televisions, stereos or microwave ovens since these objects also radiate heat when they are operating.
Humidity trays may also be used to increase the humidity around your bonsai. A humidity tray can be any shallow tray with a thin layer of small stones (aquarium gravel) placed on the bottom of the tray. Keep enough water in the tray to just cover the stones. As the water evaporates, it will provide a more humid environment around your tree. Remember that misting and humidity trays are not a substitute for watering.
Repotting
Your bonsai tree should be repotted every 1 to 2 years in early spring or late summer until the tree is about 10 years old. For trees over 10 years of age, repot every 3 to 5 years. A good indicator that your tree is becoming potbound and needs repotting is when the soil dry out more quickly between waterings. Use a well-drained soil mix when repotting.
Pruning and Pinching
To maintain dense, full growth, pinch off the terminal buds when the new growth reaches 1/2 to 1 inch. This technique will force more side branches to develop, forming dense masses of foliage. Pinching may need to be done several times during the growing season to maintain and develop the desired canopy density.
Pruning is the cutting or removal of unwanted twigs or branches to maintain the desired growth habit of you bonsai. Pruning shears or scissors may be used to prune you tree. Remember to leave a clean cut when pruning, this will encourage rapid healing of the pruning cut.
Seasonal Care
SPRING
To start forcing growth early in the season, we remove the tree from its winter storage to a cool, well lighted place out of direct sunlight. Find a spot where night temperatures are cooler than day temperatures (35-40F night minimum). This method simulates typical spring weather, providing a natural growth cycle and results in healthy, steady new growth. Once the leaves flush out in spring we begin fertilizing with diluted fish or fish/seaweed emulsion once every 2-3 weeks. Otherwise you can just wait until about March when the first buds begin showing signs of swelling and move them directly outside once again to grow in tandem with the native trees.
SUMMER
Keep the tree growing strong by placing it outside in dappled shade. Check for water daily especially during hot temperatures. If you are experiencing a cool, cloudy summer (as we did in Maine in 2000) you will not be watering as frequently and as a result the fertilization schedule can be stretched out to 1x every 3-4 weeks. During hot dry summers (like the one we had in 1999) you may find that you need to water every day and that much watering leaching nutrients from the soil more rapidly, requiring more frequent fertilization of approximately once every 2 weeks.
Keep an eye out for pests and diseases as they are very prevalant this time of year. If you find bugs you may want to check these links~ Insects on the Web or Ecological Garden Projects ~for more information.
AUTUMN
Finish summer fertilization by late August or early September. This will help the plant prepare for the leaf drop ahead.Late season applications of nitrogen can cause late season growth which will not harden off before winter. Application of rock phosphate or greensand (potassium) can be applied now. These elements will strengthen the root system and aid in flower bud formaton for the following year.
With cooler nights you may find that you don''t need to water quite as frequently. Water as needed when the soil dries out. Most of all enjoy the wonderful flush of autumn reds, oranges and yellows on deciduous bonsai which make them all the more exciting to grow. Leave the tree outside until it has completely dropped all its leaves.
Before putting your trees away you should scour it again for any signs of pests or diseases. Trees put away with these problems will usually start the new season with these same problems.
WINTER
Once the tree has become fully dormant, with no leaves or new swelling buds, it can be moved into its winter bed. The purpose of this is to ensure that the fragile roots do not suffer winter kill from the extreme cold and second to ensure that the pots don''t expand with the frozen soil and break. See Placement and Temperature above.
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