Section 18-104. Trees and vegetation; jurisdiction

The planting, care and
  cultivation of all trees and other forms of vegetation in streets  shall
  be  under  the  exclusive  jurisdiction  of  the commissioner, except as
  otherwise provided in section 18-105 of this title. The commissioner  is
  authorized  to  use  such  portions of the parks, for the cultivation of
  tree plants, as he or she  may  set  apart  for  that  purpose,  without
  detriment  to  the  parks  in  which  such nurseries are established, to
  enable him or her at all times to have tree plants  adapted  for  growth
  under the varying conditions of soil and surroundings in streets.