My magnolia plant
I was given a magnolia plant for my birthday in May. I repotted it fairly quick into a bigger pot, but since I have had it, the leaves are going ever so yellow/brown and falling off. I have fed it from time to time, I have got it in a nice sunny position, but trying hard with but really don't want to lose it.
Do you know the type of Magnolia Tree that you were given?
I will assume that it is a Star Magnolia, as this is the most likely grown and hardy in your growing area.
Growing Magnolia in containers can be quite tricky as they have an extensive root system and grows quickly.
You need to choose a container that is about 1 foot for every inch of the diameter of your mature tree.
So if the mature Magnolia will have a 4 inch trunk you should have a 4 ft wide and 4 ft deep container.
The container needs to have plenty of drainage holes.
The tree needs full sun for at least 8 hours a day.
Fertilize monthly with an acid fertilizer that is specially made for Magnolia.
Water evenly and when the top couple of inches of soil are dry.
Here are some links with more information.