Bonsai Fertilizers

Bonsai Tree Feeding & Fertilizers

Bonsai gardening is a quasi- meditative practice, with focus often on methods, shapes and arrangements. The aesthetic is unique and followed in a number of interpretations. However, the health and growth of the plant or tree is essential or everything else becomes meaningless or without purpose. For a vibrant, thriving bonsai, the gardener has to be very attentive to its needs. Light, temperature and water are among the primary concerns that have to be very closely regulated and adjusted for the environment to be optimal. Sometimes, even the most attendant gardener needs outside assistance in the form of fertilizer and other chemical or synthetic products to keep their bonsai garden healthy and free of infection or infestation.

Why Bonsai Trees Need Nutrients

Regular trees can usually grow their roots deep into soil and draw out all of the nutrients they need. Bonsai, however, are usually potted more for the aesthetic than practical value and don’t have enough room or soil to keep expanding into the ground. Their diets need to be supplemented to compensate for the lack of soil. That is where fertilizers come in. They provide the minerals and vitamins necessary to turn carbon dioxide and water into sustenance through photosynthesis. The three most important elements that will assist the bonsai in producing its own food are Nitrogen, Phosphorous and Potassium. Each of these helps the plants in its own particular way.

Important Elements For Bonsai

Nitrogen will help the bonsai continue to steadily grow its stems and produce leaves. Potassium will assist the plant with the production of flowers and fruits. Phosphorous strengthens and nourishes the roots to push them to grow. Each one needs to be present in a different amount, with different ratios to one another depending on the type of tree, soil and time of year. Indoor plants need to be fertilized all year, often dependent on the local environment (and waiting one month after repotting plus changing or altering for a sick or infested tree).

The Right Amount of Feed

The bonsai’s soil, type and depth, will largely change the amount of fertilizer or “feed” that it receives. The right feed will always contain nitrogen, phosphorous acid and potash (salts that contain potassium in liquid form) to transmit the main elements required. In addition for bonsai trees, it is recommended the fertilizer also contain “chelated” iron. This means the iron went through a chemical process called chelation to bind it to another substance, usually an amino acid. The cell membrane is more receptive to the amino acid, so the chelation allows the iron is able to pass into the cell where it is needed.


Before fertilizing, it is best to water the tree as you normally would, then add the fertilizer to the bonsai at about half the strength recommended by the manufacturer. More can be added if the gardener sees signs that the bonsai needs more nourishment. The goal is let the plant use the soil naturally as much as possible. Also, too much fertilizer can be toxic to the tree and its environment. Changing brands is a good idea as well, because different brands have different amounts of trace minerals and additives that can help the soil. Also beneficial for the bonsai is to add an additional supplement of vitamins and mineral like Superthrive. Slow release granules put on top of the soil can also make the process easier. A covering of the granules is placed evenly across the surface and the appropriate nutrients are released little by little with each watering.

Disease and Insect Infestation

Another big concern which affects both the health of the bonsai tree and the aesthetic is the prevention of disease and insect infestation. Bonsai are just as vulnerable to any other tree to fungus, bugs and other bacteria. They do tend to avoid many of the prevalent outdoor sicknesses because of their constant care and because a majority are indoors. They do still require preventative, and sometimes curative, measures. The best preventative acts are to just ensure the bonsai is receiving the optimal light, air and water. This is usually possible through close observation and adjustment by the gardener. Then, the soil should be kept clean of any debris such as dead leaves, weeds or other debris. Over-watering and standing water will also attract different bugs and should be avoided.

Insecticidal Sprays

For extra protection, insecticidal sprays can be added to the tree and its leaves. It should be one that is safe for people and animals and that keeps out the widest variety of bugs and fungi. Follow the directions and apply more than once, as most direct, but the gardener can be a bit more sparing than the directions usually say to. There are other products that can be used as needed, depending on the type of tree and the climate, like Bonsai cut dressing which will heal the tree’s wounds or leaf shine spray or moss spores, both of which improve the deep greens and the appearance of the surface of the leaves. Once the gardener has seen to the health of the tree, then the focus can successfully return to the aesthetics of it.