Bonsai trees need to be fed nutrients just like all living things. When it comes to feeding, just don’t overdo it, because too much of nutrients will kill your tree just as surely as too little nutrients would. Your bonsai tree needs feeding only because it is constantly growing, and a little of the nutrients in the soil always get washed away with each watering. Hence, regular feeding is important.
Bonsai ‘food’ or fertilizer can readily be obtained from a local nursery or gardening section, or purchased online. The most common type contains NPK, nitrogen (N), phosphates (P) and potassium (K). The last is usually in the form of potash, a material made from the ashes of wood and plants. Beyond these three, bonsai need a number of other nutrients, including iron (Fe) and vitamins (especially B-vitamins).
- Nitrogen (N) – Promotes growth of leaves. Excess nitrogen diminishes the immune system of the tree and excessive nitrogen will cause the leaves to be undeveloped and yellow.
- Phosphorus (P) – Promotes growth of roots and flowers. Trees do not uptake excessive phosphorus, so the only danger is a lack of it, which is characterized by reddish hued leaves.
- Potassium (K) – Promotes the growth of wood, flowers and fruit. A lack of potassium results in brown spots on the leaves.
The types of bonsai fertilizer available are always either in organic or inorganic form. The organic form can be homegrown made from a few common ingredients, whilst the inorganic form like pellets or granules (like Osmocote) provide timed release of nutrients into the soil, and can be left in the soil to slowly release nutrients over a period of several weeks at a time.
If you want to provide homegrown organic B-complex fertilizer for your bonsai tree, beer may make a good home-recipe substitute, since it contains several B vitamins. The risk is that, unless the alcohol content is very low, you can damage the tree. Be sure to use a weak American beer and dilute it to at least half-beer, half-water before using.
The benefit of using this unique home-brewed fertilizer is that it can encourage microbes to thrive in the soil. These microorganisms help to stabilize the PH of the soil and provide partial protection against harmful bacteria, just like in the case of the human intestinal gut; here we humans rely on good bacteria to cancel out the bad bacteria, without which our health would suffer. I know this may sound unusual, but beer does make a good fertilizer in gardening. The presence of microbes also helps buffer up the soil against wild PH swings.
The growth phase of your bonsai tree is the time when it needs regular feeding. Generally, spring to late summer is the feeding time for the production of leaves and twigs, and autumn is the time for root development, during which time you should provide a low nitrogen content based fertilizer to assist in root development.