Basic file parts of fertilizer
The three basic elements of any fertilizer are Nitrogen (N), Phosphorous (P) and Potassium (K, for Kalium), with each element serving different purposes. Nitrogen increases growth of leaves and stems (growth above ground), Phosphorus encourages healthy root growth and growth of fruits and flowers, Potassium promotes overall plant health. Sometimes different ratios of NPK are being used for different trees at different times of the year, though increasingly experts recommend using the same product throughout. Apart from the three macronutrients (NPK), fertilizers often include a range of micronutrients like Iron, Manganese, Boron, Molybdenum, Zinc and Copper.
When should I apply fertilizer?
Most Bonsai trees should be fertilized during the entire growth season of the tree; from early spring till mid autumn.
Older and more mature trees are often fertilized less frequently, also depending on the species, the time of year, the stage of development and health of the tree. Indoor trees can be fertilized around the year.
How often should I repot?
It depends on the size of container/pot and tree species how often a Bonsai tree needs to be repotted. Fast growing trees need to be repotted every two years (sometimes even every year), while older, more mature trees need to be repotted every three to five years. Do not repot on a routine, instead check on your trees every early spring by carefully removing the tree from its pot. A Bonsai needs to be repotted when the roots circle around the root system. When the roots are still contained in soil wait another year before checking again.
Repotting work normally needs to be done during the early spring; when the tree is still in dormancy. This way the somewhat damaging effect of repotting on a tree is reduced to a minimum, as the tree does not yet have to sustain a full-grown foliage. Repotting in early spring will also ensure that damage done to the root system will be repaired soon, as soon as the tree starts growing.
As mentioned previously, how often a Bonsai tree needs to be watered depends on too many factors to provide an exact guideline. Instead, you need to observe your trees individually. The following general guidelines will help you to get Bonsai watering right:
- Water your trees when the soil gets slightly dry
This means you should not water your tree when the soil is still wet but only when it feels slightly dry; use your fingers to check the soil at around 0.4’’ (one centimeter) deep. But never let a tree dry out completely! Once you get more experienced you will be able to see (instead of feel) when a tree needs watering.
- Never water on a routine
Keep observing your trees individually, instead of watering them on a daily routine, until you know exactly what you are doing.
- Use the right soil-mixture
The soil-mixture greatly influences how often trees need to be watered, for most Bonsai trees a mixture of akadama, pumice and lava rock mixed together in a ratio of ½ to ¼ to ¼ should be fine. However, use a mixture that retains more water (by using more akadama, or even potting compost) when you cannot water your trees that regularly.