They're very intolerant of wet feet, so your soil should be one that you can water to beyond saturation, to the point where you are flushing accumulating salts from the soil each time you water, without having to worry the soil will remain soggy so long it limits root function and causes the cyclic death & regeneration of fine roots, or worse, causes root rot. For best results, that should be the minimum standard for all your plants, but particularly the ones that don't do well in wet soils, like aralia. If you want more info about soils, let me know.

Also, the best time to repot your tree is between Father's Day and July 4th.

Al

Thank you so much Al. I was thinking of making my own soil mix. I was told to use a combination of light topsoil and leafgro or peat moss so it would not compact around the roots. What do you suggest?

You would be much better off if you eliminated topsoil from your list of potential ingredients and started thinking along the lines of obtaining a chunky material to base your soils on. A huge % of the problems growers arrive here seeking resolution for are descendants of (poor) soil choice. How well a plant is able to defend itself is a byproduct of its metabolic rate, so even insect and disease issues are often the result of a plant's diminished ability to defend itself, caused by a depressed metabolism resultant of poor root health.

This link has some basic information that will help you avoid all the common pitfalls indoor gardeners most often encounter.

Also

This link has information, a little more technical, that will help you understand how water behaves in container soils. The info probably represents the largest step forward a container gardener can take at any one time. I hope you find the motivation to read and understand it. It will make a significant difference in the amount of reward you get for your efforts.

Al