What does Judges 9:14 mean?

Shouting from a mountain to the town crowning his murderous brother, Abimelech, Jotham continues his fable (Judges 9:6–13). Jotham's fable has followed the trees as they look for a king. They have been turned down by the olive tree, who refuses to stop producing its abundant and honored oil. They have been rejected by the fig tree who will not leave behind its sweetness and good fruit. Even the grape vine refused to give up the wine business to "hold sway" over the trees. All three are valuable and capable, so they don't seek power over others.

Since they can't convince a "good" plant to be king, the trees turn to something wretched: the bramble.

This plant is identified with a Hebrew word that literally means "piercing" or "thorns." Scholars associate this with a genus known as lycium, which often have thin stems, bothersome thorns, and little useful fruit. In the context of Jotham's era, these were weeds. Unlike the other trees, the bramble produces nothing good or positive or healthy. It yields only irritating spikes. Modern persons might see such a plant and call it a "thornbush" or "pricker bush;" these plants have more aggressive spikes than the fuzzy irritants on thistles and nettles. They're also prone to drying out and becoming a fire hazard.

Unlike the other trees, the bramble is not productive or useful, or valuable. It has nothing better to do, so it will say yes to an offer of power over others. Clearly, Jotham is making a point about Abimelech and the terrible mistake being made by Shechem. Here, that message starts to materialize.