In chapter 17, Ezekiel uses a somewhat confusing allegory to describe some political happenings. King Nebuchadnezzar of Babylon is represented by a great eagle who takes a branch from the highest cedar in Lebanon. The branch represents King Jehoiachin and "Lebanon" is actually Jerusalem, while the cedar is the House of David. Are you with us so far?
Then Eagle-Nebuchadnezzar drops a seed from the House of David cedar—meaning King Zedekiah, left to rule in Jerusalem—which then grows into a vine which reaches out towards another great eagle. This symbolizes Zedekiah reaching towards Egypt, trying to make it an ally:
There was another great eagle, with great wings and much plumage. And see! This vine stretched out its roots toward him; it shot out its branches toward him, so that he might water it. From the bed where it was planted it was transplanted to good soil by abundant waters, so that it might produce branches and bear fruit and become a noble vine. (17:7-8)
God uses this allegory to show how useless it is for the House of Israel to form an alliance with Egypt. The solution to their problems is religious—rededicating themselves to God—and not political or military. Anyway, Zedekiah backed the wrong guy because Babylon ended up thrashing Egypt and Zedekiah paid a pretty steep price for it. Check out Jeremiah 52:8 for the gory details. (Never mind; we know you're busy. His sons are killed in front of him and then he gets his eyes gouged out.)