A list of acceptable tree species shall be adopted by the tree board, hereinafter referred to as "tree guide", and shall constitute the official park and street tree species approved for planting within all public areas of the city. No species other than those included in this list may be planted as street trees without written approval of the city's tree board. Street trees must conform to size and spacing guidelines established in this chapter, unless a variance is authorized by the tree board. The street tree species listed in the tree guide is not an all inclusive list. Other species which conform to the size and spacing criteria may be considered; however, invasive and generally undesirable tree species such as Russian olive shall not be authorized. The landowner shall be responsible to ensure that any species planted is maintained in such a way as to meet the purposes of this chapter; i.e., not impair access; damage utilities, sidewalks, or pavement; or create a public safety hazard. (Ord. 789, 4-1-2014)