Unlike regular plants wherein the roots spread out wide in the soil to gather all the nutrients, a bonsai plant is unable to do so due to the restrictions of the container. As a result the soil of a bonsai plant needs to be replenished with a suitable bonsai fertilizer for apt nutrition.
Bonsai plants need regular pruning all year round to maintain their design and small stature. The roots too are pruned regularly for maintaining the look of a bonsai. Regular watering and consumption by the bonsai leaves the soil devoid of suitable nutrients and as the result the plant suffers if the soil is not made fertile again using a good bonsai fertilizer. The fertilizer would help maintain the nutritional content of the soil and help the bonsai in being healthy. Repotting of bonsai is also done due to the fact that the soil becomes devoid of suitable nutrients after a while
Every plant uses oxygen, carbon and hydrogen from the atmosphere and water and nutrients from the soil for producing of food i.e. starch and sugars. The chemicals present in the soil are vital for the plants to be able to produce proteins, amino acids, enzymes and vitamins. Naturally soil gets all these nutrients from dead organic matter and gets replenished regularly but in case of a bonsai soil the nutrients get absorbed by the bonsai plant within no time. A suitable bonsai fertilizer would help provide the soil with all the required nutrients.
For planting bonsai plants inorganic soils like Japanese clays, Biosorb or Seramis are preferred. However, these soils are found to be lacking in potassium, nitrogen and phosphorous. As these elements are vital for a bonsai to grow healthily it is essential to replenish the soil with a bonsai fertilizer that is rich in these elements. Apart from these main elements there are some trace elements found in soils that are present in small quantities but are extremely important for the bonsai. A good fertilizer can help the soil get back these trace elements too.
Nitrogen is vital for healthy leaves, phosphorous for healthy root system and potassium for good flowers and fruits. It is not required to invest in some special bonsai fertilizer, as your regular plant fertilizer would suffice too. The main consideration should be the nutritional contents of the fertilizer and if it meets the requirements or not. When purchasing the fertilizer for your bonsai, check the content of nitrogen, potassium and phosphorous that is generally referred to as the NPK content.
Also note any other nutrients that have been added to the bonsai fertilizer. You may find the following symbols for these elements – Nitrogen may be referred to as “N”, potassium as “P2O5” and phosphorous as “K20”. Depending on your requirements you may choose to have a fertilizer with higher content of any of these elements. E.g.: If you want better flowers and fruits opt for higher potassium in the fertilizer and so on.
The best combination of a bonsai fertilizer is when all three nutrients are available in equal quantities that are referred on the packaging as 10:10:10. If you are using a soluble fertilizer apply the fertilizer all over the soil surface till the soil stops absorbing it and the excess gets drained out.