chemical fertilizer: hazardous or not?

No, I have done it from spring to fall and yet, it was very stable.
On the contrary, I have read what you wrote about your losses but in fact without EC measures your interpretation is a pure intellectual construct (that could be subjected to equally "fact-unbased" criticism to refute it).

I have actually lost two trees due to the use of osmocote but the actual scenario that leaded to these losses is far different from the story that we can sometimes read in the bonsai forums.

As far as I know, I have never lost a tree from using Osmocote. However, there is a similar product called Nutracote, which is not temperature based, and is recommended for use with bonsai.
Iris

and is recommended for use with bonsai.

By who(m)?

JimLewis wrote:

and is recommended for use with bonsai.

By who(m)?

Pauline Muth, anyway.
I can dig up the references for fish emulsion and seaweed extract, if anyone is interested.
Superthrive has never been scientifically tested, probably because Thompson won't release the formula.
Iris

bonsaisr wrote:As far as I know, I have never lost a tree from using Osmocote. However, there is a similar product called Nutracote, which is not temperature based,
Iris

Wouldn't be rather "Nutricote" ? If so, this is the first of all "*cote" fertilizers, the product of Asahi Chemicals (guess the country of origin ) and it is also temperature based.
I used to use it because it was really cheaper than osmocote but I stopped using it because when empty, balls don't break like osmocote and as I recycle my lava rock the proportion of nutricote balls was more important each year. BTW, the one I bought had no minors elements the consequence of which was absolutely imperceptible.

The temperature controlled release is something rather nice as root mineral uptake increases with temperature up to about 35/40°C . Above it is rather an annoyance and one must make sure to increase also watering to get the salts under safe limits. But as Iris's experience illustrates it is usually a no-brainer.

There is also - Multicote - and from the large bags the print says Israel.

Quite a range - 2 to 2.5 months, 5 to 6 months, and 8 to 10 months, with micro nutrients. I haven't lost anything using the stuff over the last 2 to 3 years. I use the 8 to 10 months @ 30 deg.c [ 86 deg.F ] in the rainy season -14-7-14 + 2mgo - June to January 2nd, when I repot. For February to May, I use a weak lawn fertilizer 1/3 strength into moist soil [ Supergreen used to be I believe Phostrogen - 38 - 5 - 5 ] to hold the green and keep the growth even. Placement is full sun for those that can take it.
Until.
Khaimraj

*Multicote -The recommended use is for a 6 inch pot [ 15 cm ] 2 tbs. - I don't use this much. More like a max. of 2 tsp. My compost is supposed to handle most of the feeding.

Alain Bertrand wrote:

bonsaisr wrote:As far as I know, I have never lost a tree from using Osmocote. However, there is a similar product called Nutracote,
Iris

Wouldn't be rather "Nutricote" ?

Even fanatical spelling maven monkeys fall out of trees.
Iris