Subjects of civil strife; whatever rouses citizens to rise in arms. The allusion is to the dragon that guarded the well of A'res. Cadmus slew it, and sowed some of the teeth, from which sprang up the men called Spartans, who all killed each other except five, who were the ancestors of the Thebans. Those teeth which Cadmus did not sow came to the possession of Æe'tes, King of Colchis; and one of the tasks he enjoined Jason was to sow these teeth and slay the armed warriors that rose therefrom.
“Citizens rising from the soil, richly sown with dragon's teeth, for the rights of their several states.” —The Times.
To sow dragons' teeth. To foment contentions; to stir up strife or war. The reference is to the classical story of Jason or that of Cadmus, both of whom sowed the teeth of a dragon which he had slain, and from these teeth sprang up armies of fighting men, who attacked each other in fierce fight. Of course, the figure means that quarrels often arise out of a contention supposed to have been allayed (or slain). The Philistines sowed dragons' teeth when they took Samson, bound him, and put out his eyes. The ancient Britons sowed dragons' teeth when they massacred the Danes on St. Bryce's Day.
Source: Dictionary of Phrase and Fable, E. Cobham Brewer, 1894