It is hereby declared unlawful for any person to plant, grow, keep or maintain, or cause to be planted, grown, kept, or maintained, any hedge, bush or shrubbery of any kind or nature more than three feet in height above the roadway within the triangle formed by the adjacent side lines of two intersecting streets and the line joining points distant thirty feet on each side line from their point of intersection. For the purpose of this section, "side line" of street shall mean the property line.