Magnolia tree rescue

I saved a magnolia tree that had been mowed down. The trunk had been about 4 inches across. I planted and fertalized the root ball, and now I have 20 shoots and plenty of healthy foliage. How and when do I go about trimming the shoots to make one trunk? The shoots are about 2 1/2 feet tall. Any help would be appreciated. Thank you. Sarah

 

Cut away the weekest shoots and leave the strongest ones.

:)

 

Thank you for your reply.... What time of year is best to cut them back? I guess that after the leaves turn and fall off.

 

Spring.