Bay seniors don’t require much convincing to appreciate the glories of Marin, but in case you need reminding, circle Saturday,June 16 on your calendar. From 10-4 the estimable Marin County Garden Conservancy invites you to visit four particularly paradisial gardens. There are two in Mill Valley, a terraced Italian hilltop and a semi-tropical eden dense with 30-foot tree ferns and palms. There is a vibrantly colorful estate in Tiburon and in Kentfield a witty collaboration with the sculptress, Marcia Donohue. Tickets, at $25 per, go fast.