Posted: 01/11/2014 at 17:35
Apple..........9" diam sounds rather large for something of 14 or 15". If your plant hasn't much of a root system now, you want to avoid surrounding it with too much compost. That way you can tend to overwater and drown what roots you do have.
It's always a bit difficult to explain exactly when you don't have the plant in front of you but........if you ensure that the roots/rootball have sufficient compost around them so they don't actually touch the sides of the pot, that is usually a reasonable guide IMO.
Once the plant starts to make new roots, then is the time to re pot using the same criteria. I find I'd prefer to re pot rather than overpot if that makes sense ?
Hope this helps and that your Avocado will do well