Colossus (Magnolia sieboldi ‘Colossus’) Posted on December 13, 2013 by Lucile Whitman Colossus is a bigger better flower for siebold Magnolia. It is still a perfect tree for a small garden if you want a white fragrant flower that never suffers frost damage. Size: 1 gallon Price: $30.00 Size: Field grown Price: $115.00