Employing Cu toxicity as a method of killing root tips and forcing bifurcation of roots has been around for a looong time. It has several downsides. See what Dr C Whitcomb, PhD, author of "Plant Production in Containers" has to say by following link below.

Al

Here is a link that might be useful: More here

Tapla,thanks for the info, but i notice that so many have info as to why they use it. My position on that is: i have several tropical tree's that need a better root system so that the roots don't get disturb for a few years and make up-potting so much easier

I grow many species of trees in containers - evergreen, tropical, temperate deciduous, ..... - and the root systems are always healthy and they always colonize the entire soil mass. Also, removing soil at repotting time is very easy.

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The soil I use:
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There is no need for the toxic Cu coatings ..... and you're probably going to find it doesn't work as well as the advertising claims.

Al