Bonsai Fertilizer - Not too much, not too little

Any growing plant will need a steady source of fertilizer for it to mature well and without complications. If you have been a long time gardening enthusiast but have only recently started on bonsai cultivation, you will find it re-assuring to know that fertilizing principles and concepts that you have been using for a long time will work just as well on bonsai. The mechanics and science behind plant growth remain the same regardless of the size of the plant you are growing so they are transferable from plant to plant.

The addition of bonsai fertilizer is necessary to provide the plant with “supplemental nutrition” otherwise lacking or not present in the soil. Typical fertilizers contain phosphorus, nitrogen, potassium and other minor elements to help the tree in performing normal growth processes. Nitrogen is the most important element when considering the color of the leaves and the rate of growth while Phosphorus is necessary for cell division and excellent root growth. Potassium regulates how efficiently a plant utilizes carbon dioxide and water, acting as a transport regulator to ensure that all parts of the tree are getting the appropriate nutrients from the soil and the bonsai fertilizer.

An important consideration when fertilizing bonsai cultures are: “How much fertilizer should I put in?” and “How frequently should I fertilize?” As to the amount of fertilizer necessary, each bonsai fertilizer type is made to provide the optimum amount of required nutrients to the plant. As such there is no golden rule that applies to every single bonsai fertilizer brand or batch. Instead, read the label and follow the supplier’s recommendation as diligently as you can. On the second question of frequency, there is a direct correlation between the amount and frequency of bonsai fertilizer you are giving to the plant. The more fertilizer you add per dose, the less frequent you will need to add bonsai fertilizers. It also follows that with smaller fertilizer amounts, you will need to fertilize more frequently. A good rule of thumb, but not always applicable, is to put in about 150-250 grams of fertilizer every one or two weeks depending on the size of the plant.

There is also a good rule for knowing when the optimum time to fertilize your bonsai is. Conventional logic holds that the best time for adding bonsai fertilizer is during the spring and summer when the plant is actively growing. New studies however have shown that it is actually more beneficial if one fertilizes starting in the summer but continue up to late fall and early winter. The plant is able to adequately store enough nutrients through the winter so it can continue growing despite the harsh conditions – as long as it is given sufficient protection from the frost. One should only stop fertilizing at the peak of the winter months up until the break of spring.

As a last note on bonsai fertilizers, the grower should note that there is such a thing as over-fertilization. This happens when a plant is getting more fertilizer than it can process. The most obvious effect is called a salt burn when the excess “salts” in the soil will draw the water away from the roots. This will cause the roots to dehydrate and die. Another effect is that it can cause runaway growth or over-growing which in the case of bonsai culture is not a very good thing to have for very obvious reasons. Make sure to follow the supplier recommendation on the bonsai fertilizer label so you are not left to guess about what’s best for your plant.

Growing bonsai can be a rewarding experience but it will take significant effort to master it for a bonsai to grow as expected. Be patient with your bonsai cultures and do not be overzealous. You will find that daily observation will tell you exactly when to fertilize so you will have a healthy growing bonsai plant.