It is now summer here in the UK, so hopefully you all have your feeding and watering regimes in place for your bonsai tree(s).
It is important to feed because:-
- Bonsai trees restricted to receiving nutrients provided for them by their owners
- Bonsai trees cannot access wider nutrient resources from beyond their bonsai pots
- Bonsai trees still need food to grow and develop to remain healthy, and it is a myth that in order to make a bonsai tree you do not feed them
- Feeding is essential to aid with the trees functions biologically and physiologically
- Feeding ensure your bonsai trees will live long and prosper
- It aids with fruiting and flowering
- It strengthens the tree to aid with fighting off pests and diseases
Ways to feed your bonsai tree
- Slow release fertilizer in the soil within the bonsai pot
- Liquid feed applied whilst watering
- Foliar spray applied to the leaves
- Slow release fertliser applied to onto the soil
- Organic matter in soil
What to feed your bonsai
A balanced fertliser based around the 3 key primary Macro nutrients which are:-
N – Nitrogen
K – Potassium
The main secondary nutrients include:-
- Calcium (Ca)
- Magnesium (Mg)
- Sulfur (S)
Plus a range of the essential Micro nutrients or trace elements which include:-
- Boron (B)
- Copper (Cu)
- Chloride (Cl)
- Iron (Fe)
- Manganese (Mn)
- Molyndenum (Mo)
- Zinc (Zn)
So try to feed a balanced feed which has a range of nutrients but is not high in any particular one nutrient, and a balanced fertiliser would be 7,7,7 of N,P,K with trace elements of the micro nutrients.
What affects how much nutrient your tree can access?
- Size of pot as this limits the quantity of soil in the pot.
- Soil type as some soils contain nutrients already while others need nutrients added like if you use akadama you will need to add nutrients to the soil while if you use a compost based soil this will already contain a level of nutrients for the bonsai tree to access.
- Soil pH, as the more acidic the soil pH the less nutrients are available for the tree as well as the more alkaline the soil is the less nutrients are available. The optimum pH to have is 6.0 to 6.5.
- Water levels, as nutrients are more available in moist soil conditions, when the soil is damp not dry but also not waterlogged.
- Light levels will reduce the nutrient uptake as the level of photosynthesis is slower in low light levels.
- Temperature as the higher the temperature the less the tree can photosynthesis as most start to try to conserve water loss by closing their stomata which slows or stops nutrient uptake. Temperatures above 24 degrees Celsius are when nutrient uptake slows and by 30 degrees Celsius nutrient uptake ceases for most broadleaf bonsai trees. Specially adapted species can still continue to take up nutrients but are the exception.
How much to feed?
This will vary on whether your bonsai trees are deficient in any of the macro or micro nutrients, for example if your soil pH is too acidic then you can fertilizer with higher calcium or magnesium to aid with changing the pH to a more alkaline soil. Furthermore, if the soil lacks organic matter by adding sulfur can aid with this.
The quantity applied for bonsai should not be full strength as the trees are not bale to cope with the concentrations as they are confined to a bonsai pot so excess nutrient cannot diffuse into a wider soil area.
Quarter strength or less of the recommended amount on the label works well and the key to fertlising is little and often.
When to feed?
The key time to feed is during the growing season, early Spring through to Autumn. The reason for this is that the bonsai tree needs food during this active growing period and also for setting down stored energy to get it through the winter period.
Food is important for flowering and fruiting trees as this takes a lot of energy from the trees stored reserves and feeding during this period is good to maintain health.
Examples of some of the types of fertilizer commonly used on bonsai trees
- Seaweed liquid feed
- Tomorite liquid feed
- Chempak range granules for liquid feed
- Miracle grow slow release granules or liquid feed
- Fish emulsion liquid feed
- Bio gold slow release blocks
- Naruko slow release pellets
- Green dream slow release pellets
- Maxi crop liquid feed
Depending on who you ask to how often is recommended. Some bonsai growers feed with every watering via liquid feeding, others set up a weekly feeding or fortnightly feeding regimes.
Feed your bonsai trees as often as they need it is the best way, but if in doubt weekly would not be too problematic for them.
If you have slow release within the bonsai pots they will have access to nutrients, likewise if your soil contains organic matter. Another way is to place slow release on the surface of the soil in basket containers and this allows a small release of nutrients at each watering.
If they are showing signs of being nutrient deficient then start increasing the feeding frequency.
When not to feed
- During dormant period ie when the trees have no leaves on
- Immediately after re-potting
- When the tree is stressed or showing other problems
- When temperatures are over 30 degrees Celsius as it is too hot for nutrient uptake and can cause more stress and damage to the bonsai tree, but instead increase your watering regime to ensure that your bonsai tree does not suffer from lack of water and become drought stressed
- When the soil is dry, water first without feed and then apply the feed
What happens if you do not feed your bonsai
- It will still grow for a while but will use up its stored reserves of nutrients and become weak
- It won’t grow fast so there will be reduced pruning opportunities and may take longer to develop the shape and style you want
- It will be more stunted and the trunk will grow only by millimeters at a time
- You will have fewer leaves and ramification of the crown will be slow and may never be achieved
- It will take longer to seal over pruning wounds if not at all
- It won’t remain healthy as it will lack vital nutrients for normal development
- It may have more dead branches and die back plus be more prone to pests and diseases
- It could ultimately starve to death and die
Therefore ensure you feed your bonsai trees to maintain a good healthy tree for the future.