Technical question I know.
I'm referring to the various "soil conditioners" people put in the hole when they plant a tree*.
Save your money. They're unnecessary.
In fact they can be counter-productive.
Put it this way, if it's all cosy and easy at mum and dad's, would you want to leave home?
Tree roots are the same.
Supply them with lots of moisture and nutrients right at their fingertips and those little darlings will tend to stay put.
You've got to entice them out. Add some complete fertiliser to the hole to get them going but then progressively fertilise further away from the trunk as the roots begin to poke their noses out into the wide old world.
Take the same approach with the watering and you'll end up with a tree able to stand on it's own two feet within three years or so.
Oh, and keep the grass well away from them. Grass pinches all the nutrients and water and you're back to square one.
And "oh" again: USE A SOIL WETTING AGENT. If you're on the Perth sand plain you will almost certainly have hydrophobic soil. I can't tell you how many times someone's asked me to consult on a struggling tree which they can't understand because "I water it all the time". I kneel down, stick my fingers in the sand and it's bone dry a few centimetres under. The water is just moving laterally, not vertically. Remember, the water doesn't just have to go ON folks, it has to go IN!
Anyway, there you go - how to grow a tree 101.
No goo in sight :)
* Please note I'm talking about trees here - mileage may vary with small plants and turf ;)