Will cut off head and tail - This is a proverbial expression, which is explained in the following verse; see also Deuteronomy 28:13-14. The head is often used to denote those in honor and authority. The tail is an expression applicable to the lower ranks, and would commonly indicate more than simply the common people. It would imply contempt; a state of great abjectness and meanness.
Branch and rush - This is also a proverbial expression, meaning the highest and lowest; see the note at Isaiah 19:15. The word here translated branch, means properly the bough or top of the palm tree. The palm grew to a great height before it gave out any branches, and hence, the image is a beautiful one to denote those high in office and authority. The word rush means the coarse, long-jointed reed, that grows in marshes - an apt emblem of the base and worthless classes of society.