A rare word translated as "said" is used in this verse, but Jesus only uses this word in four verses, always to describe a master talking to a servant. The sense is a stronger statement than one of the common words for "said."
The verb translated as "root up/uproot" is a rare one in ancient Greek. It appears for the first time in the Septuagint, where it is used only three times to describe "uprooting" whole civilizations. It means literally "away from root" so it is easy to understand, but someone familiar with the OT may have recognized the analogy here.
Christ's Words in Matthew as a Guide to 40 Days of Prayer.