Why we fertilize bonsai
Since bonsai tree’s live in small pots and the roots can not grow deep into the soil to have an unlimited access to nutrients and moisture
it is important that we provide our bonsai with nutrients to grow and sustain live in a pot.
there are allot of different types of fertilizer they come in liquid form or solid slow release pellets, powder and organic or synthetic.
to apply the fertilizer the right way to aid our bonsai some basic knowledge about how fertilizer works is the key to success.
Main ingredients and their purpose.
all the available fertilizers on the market are usually made up out of the three major nutrients that plants need: nitrogen, phosphorus, and potassium.
These are referred to by the initials of their chemical symbols: N (Nitrogen), P (Phosphorus), and K (Potassium).
these three ingredients are always shown on the package description of the fertilizer as the NPK value, as example:
NPK 5-8-7 means 5 parts nitrogen 8 parts phosphorus and 7 parts potassium.
(N)Nitrogen increases the growth of the leaves and stems or the growth above ground.
(P)Phosphorus contributes to healthy root growth and the growth of fruits and flowers.
(K)Potassium enhances the overall plant health.
Bonsai practitioners often use different ratios of NPK for different type of trees or stages the trees are in.
as example for a flowering species like azalea one can use a fertilizer with a higher P (phosphorus) value to aid the tree in producing strong healthy flowers or a tree in development that needs allot of growth to thicken the trunk or the branches a fertilizer with higher N (nitrogen) can help the tree in providing nutrients for stronger growth but when a tree is in the refining stage and does not need to grow that strong a lower N (nitrogen) in the fertilizer is often a better choice.
Apart from the three macronutrients (NPK), fertilizers can also include a range of micronutrients like Iron, Manganese, Boron, Molybdenum, Zinc, and Copper which each also have their own function and sometimes need to be added.
as example if a tree has a iron deficiency the leaves or needles show a yellowish color by adding a product containing more iron to the soil the leaves will turn back to a healthy vibrant green color this will in return restore the photosynthesis property’s of the foliage.
there is much more in depth information about fertilizer to be found but this basic information should get you started picking a fertilizer for your tree’s and start feeding them
When or when not to apply fertilizer?
Bonsai should be fertilized during the growing season early spring through mid-fall.
Tropical species that are kept indoors grow year round and so can be fertilized year round
Never fertilize Sick, Weak, Dormant, or freshly repotted bonsai
How to choose the right fertilizer
It is important to choose the right fertilizer for your Bonsai and apply the right quantities.
In general using a balanced fertilizer throughout the growing season, and slowly decreasing the amount applied towards the end of the growing season is good way to fertilize your trees.
The fertilizer you choose should also depend on the developmental stage of your trees.
A Bonsai in early development needs strong growth, so we need a relatively strong fertilizer.
For a Bonsai in late development we desire balanced growth for fine ramification, and a balanced fertilizer would be recommended.
Subtropical tree species are often kept indoors and don’t experience seasonal changes. They grow year-round so they can be fertilized year round but organic fertilizer often comes with a smell so allot of people use liquid fertilizer for that reason.
there are allot of brands that sell “special” bonsai fertilizer and those are often balanced the right way to aid our tree’s but they usually also come with a higher price tag and regular fertilizer of other brands are often just as good to serve the same purpose but my personal preference goes to using organic granular based fertilizer.
How to apply fertilizer
When applying any fertilizer always follow the description of the packaging for the interval and amount of fertilizer to apply, to much fertilizer might be damaging the roots or builds up salt deposits in the soil which are not beneficial for your tree, using a proper bonsai soil helps reducing the chance of salt deposits building up in your pot and reduces the risks of over fertilizing.
Liquid fertilizer:
prepare a watering can with the packaging described dose and water your tree with the dilution and repeat x given time as described on the packaging.
Organic granular based fertilizer:
during the growing season people put special fertilizer baskets on their pots or use empty paper teabags, fill those with a little sphagmum moss and fertilizer so that with each watering a little of the fertilizer will go into the soil.
some pellets or cake form fertilizer can be put directly on the soil but be aware that if you do that it doesn’t influence the draining structure of your soil by clogging up the voids with broken down fertilizer so I personally do not recommend doing this.
Foliage feed fertilizer:
Some tree species also have the ability to take up moisture and nutrients trough the foliage so some practitioners like to Foliar feed their trees as a addition to the regular fertilizing schedule to give them a little extra nutrients.
these fertilizer are often not as strong as regular fertilizer as that would result in damaging the foliage when applied.
one common foliage fertilizer is fish emulsion its diluted in a pressure sprayer according the packaging description and is then misted on to the foliage and repeated trough the season according the package description.
don’t apply foliar feed during full sun or on fresh new foliage as that might be harmful and can cause leaf burn.
There is allot more in depth information to be found online which is worth looking up but these fundamental basics described above should be in my opinion be enough to get you started picking a good fertilizer and at the right time start fertilizing your bonsai!