Bonsai fertilizer is a vital factor in successful bonsai growing.
Like many people, I used to believe that fertilizer is food for bonsai trees. After study, however, I figure out that my belief is not precisely true. Fertilizer is much more similar to vitamins rather than nutrients.
The real food for plants is carbon dioxide and water, which are converted to sugars and carbohydrates through photosynthesis process. Fertilizer acts as assistance for such biological process of food production in plants.
Three basic elements of any fertilizer are Nitrogen (N), Phosphorus (P), and Potassium (K). Each of them serves different purposes.
Fertilize during the entire growth season of the tree; from early spring till mid autumn. Indoor trees can be fertilized around the year. Although sometimes disputed, do not fertilize repotted trees for about a month; also do not fertilize sick trees.
On each bag of fertilizer, there is a ratio, such as 10-20-10 or 29-6-4. Do you know the meaning of those numbers? Well, they indicate the percentage by weight of three major components, which are Nitrogen (N), Phosphorus (P), and Potassium (K).
Yet, the "N-P-K" values are not reported in a straightforward manner, but in terms of their correlative compounds: Nitrogen (N), phosphate (P2O5), and soluble potash (K2O). Then, a 10-20-10 fertilizer has 10% nitrogen, 20% available phosphate (P2O5) and 10% soluble potash (K2O).
Different ratios of N-P-K are being used for different trees at different times of year, which is very important to take into account when fertilizing Bonsai. In most cases, you will want the fertilizer with the highest first number, the fertilizer that contains the highest percentage of nitrogen, such as a 24-8-4.
A bag of bonsai fertilizer that only has two numbers, such as 20-0-20, or one number, such as 34-0-0, is an incomplete fertilizer because it is missing one or two of the three major elements.
To promote good flower or fruit production, use a fertilizer with the middle number higher than the first. If you want to toughen up your plants for better drought, disease, or winter resistance, use a fertilizer with the last number being the highest.
You can fertilize by watering directly to the soil or by applying directly to the leaves. Never feed a bonsai tree if the soil is dry. It is recommended to first water with straight, clean water. After 10-20 minutes, you may water again with fertilizer diluted in water.
You can put the bonsai fertilizer in a spray bottle because the foliage can absorb the fertilizer, but bear in mind that the effect is more rapid evaporation. It is very important to regularly change the method of application, or the roots may become weakened if we just spray the leaves all the time.