Roof decks, patio spaces, backyards, neighborhood parks and community gardens will be part of the 16th annual South End Garden Tour from 10 a.m. to 4 p.m. Proceeds benefit the South End/Lower Roxbury Open Space Land Trust, which owns and maintains 16 community gardens. Tickets, $20, will be sold at the South End Branch of the Boston Public Library, 685 Tremont Street (Rutland Square). Advance tickets, $17, and information at (617) 437-0999 and southendgardentour.org.  This year, there is a special ticket price to members of area garden clubs.  If you purchase 5 tickets or more, the price drops to $15 per person.  This is called the “carpool discount” – just mention your affiliation with the Garden Club of the Back Bay when you call to reserve.