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. Check our care guides for specific information about when to fertilize per tree species.
Which fertilizer to choose?
It is important to choose the right fertilizer for your Bonsai plants and apply the right quantities. It is often recommended to use a fertilizer with a relatively high Nitrogen content in spring (something like NPK 10:6:6), a more balanced fertilizer (like NPK 6:6:6) in summer, and in autumn a low Nitrogen fertilizer (like NPK 3:6:6). Increasingly though, experts prefer to use a balanced fertilizer throughout the growth season, slowly decreasing the applied quantity towards the end of the growth season.
(Sub)tropical tree species are usually kept indoors and and therefore, unlike outdoor bonsai, won’t experience the change of seasons too much. Indoor Bonsai grow year-round and therefore need to be fertilized year-round as well. For indoor Bonsai we recommend a balanced liquid fertilizer, you can follow the guidelines as stated on the product packaging.
A few exceptions are worth pointing out: to encourage Bonsai to flower use a fertilizer with a high Phosphorous (P) content (like NPK 6:10:6) and for older trees you might want to use fertilizer with a slightly lower Nitrogen (N) content or reduce the quantity of fertilizer applied.
Although “Bonsai fertilizer” is fertilizer like any other, buying from (online) Bonsai shops will help you find the right NPK values. Biogold is a favorite product for many Bonsai enthusiasts, but any fertilizer with the right NPK value is perfectly fine. You can choose to use either liquid or solid fertilizer, as well as either synthetic or organic; it doesn’t matter much. But make sure to follow the application guidelines as stated on the product’s packaging.