What are peoples thoughts on making your own fertiliser for bonsai, for example using onion peel, egg shells and tea leaves?

I see no reason for doing this.

Widymaj wrote: What are peoples thoughts on making your own fertiliser for bonsai, for example using onion peel, egg shells and tea leaves?

Fertilizer is a collection of chemicals the tree needs to thrive. You can analyze the tree's requirements and mix up fertilizers to match, but it is probably faster and cheaper to buy it prepared.

I can't think of any species that needs calcium, and I don't have any idea what nutrients tea leaves have. I don't think onions would help.

Mixing up chemicals for non organic fertilizer is easy and very check. And you can get a perfect balance. However what is a perfect balance is still depated after decades of use.

When mixing organic fertilizer it is not possible to calculate the exact content because it is organically bound in a lot of different forms and different mineralisation processes needs to take place in order to make it awailable to plants. However that has not stopped a thriving production of organically growing crops all over the world. They know how to produce but not why it works.

When it comes to bonsai the mineralisation processes is vastly different from inground growing. Most of them just dont occure. So the mix has to be quite different. Bonsai artists all over the world has found some organic ingrediens work good. Fish emulsion beeing the most common i think. But I have read people having good results with nettle water and golden water. I use koi water in summer and and bat guano in authum and think that it has some benefits.

With the mineralisation in mind it is likelly to believe that a bigger persentage of what you add to the soil is taken up by the tree in non organic fertilizing than in organic.

I would just compost those items, and then use the compost for projects.

Just a side note for eggshells. All over internet i read that people crack up egg shells for calcium. But most don't know that egg shells are hard to brake down, it will take years and years and years. When you burry an egg, and dig it up after 5years, then the shell is still in perfect condition. So egg shells need to be broken down to powder dust, the most extreme tiny particals, before it would be benifitional for any plants to take up as nutrients.

Egg shell time to break down is very dependent on soil ph. I have the same problem as Rorror. My friend 200 kms from here claims it is very fast process. He lives in drained wetland with a very low ph.