What to buy?
Is your tree still in its growing phase or developing phase? Then a fertilizer with high nitrogen content is the best deal. Nitrogen will help boost leaf growth and this is essential in pruning and styling bonsai plants. If your plant or tree is in the refinement stage then you need a fertilizer with lower nitrogen levels and higher potassium and phosphorous levels to be able to maintain overall health and strength and for manufacturing fruits. You will find nitrogen level information from the N-P-K ratio on the packaging of the fertilizer.
Nitrogen is the most important element. It gives your plants their rich color and it makes them robust with strong branches and thick leaves. Strong plants can usually protect themselves naturally against bugs and other pests.
Potassium helps in making the roots and foliage strong. The plant will be more resistant to drought, bad and cold weather as well as diseases.
Phosphorous works underground to encourage the growth of strong roots.
N-P-K ratio can be numbers such as 12-6-8 or 30-10-10. Each number represents the percentage of nitrogen-potassium-phosphorous.
Too much fertilizer can also burn the roots and kill the plant. Each plant has its own requirement so you would have to inform yourself about the needs of each individual plant variety.
I hope this post will help you choose your fertilizer better. Read more on the Types of fertilizers where I describe their forms and how they can facilitate your gardening needs.