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Bonsai for beginners, Issue #013-- Bonsai Feeding
March 12, 2008
What a summer, I don't remember such a long dry spell. We needed to buy in four tank loads of water between Christmas and the end of January. I'm sure a large percentage of which was sprinkled on my bonsai.
I don't advocate stressing your trees in this way unless you are about to have to hand over yet another $200 for a tanker load of water.
Close up of flowers
Close up of roots over rock
We have had quite a few questions from you all lately about feeding your bonsai - Should I? When should I? What should I? etc
So here it is.
Bonsai FeedingShould I feed my Bonsai?
A tree that had been repotted and root pruned should be able to survive 12 months without feeding. You may however wish to boost growth or stimulate other characteristics of your tree. If you have an older tree that you do not repot each year feeding may be required.
Firstly there are several times that you should not feed.
Don't feed directly after root pruning, wait at least 8 weeks - you may use a soil mix that includes a slow release fertilizer and it will do it no harm.
Don't feed sick or diseased plants. This is one of the most common mistakes I hear through emails. "My tree was sick so I loaded it with fertilizer to try and bring it back to health." It won't if your tree is diseased, it will not be taking up food and at best the fertilizer will be leached trough and wasted, or at worst it will build up and prevent water uptake compounding the trees problems.
Don't feed during heavy rain, our pots are only small with very good drainage and if you fertilize during rainy periods, liquid fertilizer especially will be leached out. Do water before by all means, about 25% moisture level is ideal.
Don't feed during hot weather, this is not quite so obvious but at high temperatures most trees will shut down and stop taking up nutrients. Around 20 degrees C or 68 degrees F are optimal temperature for absorption.
Do feed your trees during the growing season, usually spring and summer in most temperate climates.
Plant food is broken into two major groups; macro-nutrients and micro-nutrients. Most potting mixes will provide your trees with enough of the micro-nutrients so you shouldn't need to add any. So we will talk about the macro-nutrients.
Nitrogen Plants use nitrogen to grow foliage and it is used up very quickly by most plants. Lack of nitrogen causes stunting and yellowing of older foliage. This is by no means the only thing that causes yellowing so be careful. Check your plant for other symptoms before feeding. Make sure yellowing is mainly on older growth and not on young shoots.
Phosphorus This helps promote strong root growth and will give your tree a look of maturity.
Potassium This works with the other nutrients as a catalyst. It also inhibits the nitrogen preventing it from producing too much soft wood. Potassium aids in the manufacture of sugars and starches, it also helps produce chlorophyll. It is good for fruit and flowers and builds resistance to cold.
Calcium Calcium is used to build the cell walls it also makes phosphorus and potassium more available to the plant. Don't over use it on acid loving plants like azaleas, it will make the soil alkaline.
Sulphur is part of the molecules that make up plant proteins, a deficiency may lead to weak root development and paler foliage.
Organic versus Chemical
Less chance of burning
Slower acting, won’t bolt the tree
Encourages beneficial bacteria
You can buy varying degrees of nutrients
You can get slow release (Osmocote etc)
Ease of use/no smell
Can burn trees roots
Can harm useful bacteria
Here is a recipe I got from Deborah Koreshoff's book "Bonsai Its Art, Science, History and Philosophy" that I managed to pick up on trademe. (The book is out of print) It is a great book.
3 parts soya bean meal 1 part blood and bone 1 part chicken manure 1 part wood ash 1 part fish emulsion
Place all the ingredients into a container, 4 times the volume and add water to bring it to half way. Put a lid on and leave it to bubble away for about 3 months. After it is fermented top up the bin withwater. Use one part of this mix to five parts water and dunk or water your plants thoroughly.
You can also make small fertilizer cakes from the same mixture by adding less water allowing it to evaporate. Once evaporated add plain flour to make it sticky and form it into small biscuits. Let these dry in the sun until hard. Just place these on the soil of your trees they will act as a slow release fertilizer.
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