Fertilizer basics
From BonsaiWIKI
Fertilization is one of the least understood facets of bonsai. There is a general idea that because the tree is to be dwarfed, fertilizer should be withheld to "starve" it.
In reality, all plants manufacture their own food through a process called photosynthesis. Fertilization provides needed building blocks (nitrogen, phosphorus, potassium and trace minerals) required to sustain growth. Growth may be limited in the absence of some of these critical components, but it is usually to the tree's detriment to check its growth in this way. It is a better practice to fertilize regularly, ensuring health and robust growth and control the direction and amount of growth by pinching, pruning, and repotting.
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Types of Fertilizer
Fertilizer often described as organic or inorganic. Organic fertilizer is composed of natural ingredients, and it must generally be acted on by soil borne microorganisms in order to release its nitrogen for consumption by the plant. Organics used for bonsai might be a prepackaged fermented rapeseed cake or a solution of fish emulsion.
One advantage of organic fertilizers over their chemical counterparts is that the organics encourage a wealth of microorganisms in the soil that can be beneficial to the tree by helping to buffer pH and help regulate the moisture and acidity of the soil. Organic fertilizer must generally be replenished every 4-6 weeks. Some have distinctive odors.
Inorganic fertilizer (like Miracle-gro) are chemical solutions that go to work rapidly. Some are available in pellet form (osmocote) with a time-release or water-release chemistry that will act over a longer period. They are usually odorless and go to work on the plant immediately.
The NPK Factor
Regardless of the type of fertilizer, the composition of the product can be understood by its "NPK" ratio, which is the proportions of Nitrogen (N), Phosphorus (P) and Potassium (K). In addition, because bonsai live out their lives in small containers, the addition of trace minerals can be beneficial. Yellowing leaves with prominent green veins are usually a sign that there is a problem with pH or lack of nitrogen or iron.
Acidity of the Soil
Even if these constituents are available in the soil, they may be bound up in chemical compounds that make them unavailable to the plant. Iron is a common example. Adding chelated iron or slightly reducing the pH of the soil will help, and the use of a Miracle-gro product called MirAcid may be useful in acid loving plants to help lower the pH.
How to Fertilize
Apply fertilizer during the growing season. A low-nitrogen fertilizer like bone meal may be applied in the fall and late winter to encourage development of the root system.
Rapeseed cake or cottonseed cake may be applied every 4-6 weeks during the growing season. Older cakes should be removed after approximately 8 weeks before it becomes too difficult to remove.
Fertilizer cups may be added to cover the fertilizer and help prevent insect and rodent activity.
When to Fertilize
Chemical fertilizers are much more fast acting, and extreme care should be taken during their use for the sake of your bonsai. Water-soluble, Inrganic fertilizer like Miracle-Gro can be applied at low concentrations during regular watering (see fertigation)or simply applied periodically, for example, every 2-3 weeks, at the recommended concentration. Pellet-form fertilizer like Osmocote should be applied sparingly at perhaps 1/4 to 1/3 the recommmended dosage until its effects are known to the grower.
Fertilizer is generally withheld during the hottest months of summer. Resin-coated fertilizers like Osmocote release more fertilizer at elevated temperatures. has commented that such fertilizers may be inappropriate for climates that combine elevated summer temperatures with a lot of rain.
Fertilizer may be reapplied in Fall weather. The conventional wisdom was that foliage growth should be discouraged in late fall as the tree prepares itself for winter, but this is a theory that has been debunked by Brent Walston. Craig Coussins has pointed out problems using resin-coated fertilizers in climates that combine elevated summer temperatures with a lot of rainfall.
The transition to low-nitrogen fertilizer during autumn is appropriate to help in the formation of flowers and development of the root system.
| Fertilization Terms |
| Fertilization: Foliar fertilization | Fertigation | Feeding | CEC ratio | overfertilization | fertilizer deficiency |
| NPK: Nitrogen (nitrate ammonium and urea) | Phosphorus | Potassium |
| Minors: Boron | Chlorine | Chromium | Copper | Iron | Manganese | Magnesium | Molybdenum | Sulphur | Zinc |
| Organic fertilizer: Fertilizer cake | Fish emulsion | Seaweed extract | Bat guano | Bone meal | Blood meal | Biogold | Cottonseed meal | Fish Meal | Chicken Manure | Cow Manure | Soybean Meal | Alfalfa Meal |
| Misc: Epsom Salts | Rock Dust | Gypsum |
| Inorganic fertilizer: Miracle-Gro | Miracid | Osmocote | Dyna-Gro |
| pH: Acidity | Alkalinity | Chlorosis | Vinegar | Lime |
ALTERNATE KEYWORDS: Fertiliser Fertilisation
