I suggest you use Nitrophoska Blue. Apply to the surface and around the dripline at a rate of one tablespoon per plant. This fertiliser is an excellent general garden fertiliser. I would only recommend applying on the surface after planting, if you place in the hole when planting it may burn. Also try not to apply to foliage as this will also burn. Reapply this fertiliser after six months. If your cabbage tree has brown spots on the leaves there is no need to worry as this is caused by high humidity, as our winter weather temperatures arrive these spots will disappear. For general care of your cabbage trees I suggest a light spray of Yates Super Shield this will prevent or cure insect and fungal problems.