Tea House Garden: a garden within the garden. SJG has one with the Shoseian Teahouse inside; it is run by Urasenke Foundation of Seattle, together with Tea ceremony demonstrations and presentations. Before this page is fully written, please enjoy their rich website, which includes explanation of Chado tradition.
SJG offers tours of Roji (no tea ceremony), and there are 2 left for this season:
Sept. 14 and Oct. 12 (Tues.) at 12:30 PM; they are free with Garden admission and last approximately 30 minutes.
Here is a good resource on Japanese Tea Ceremony, including different traditions of Tea Schools, history and theory.
Also a link to a PDF page from Kyoto University - it has basic explanation about Roji: Entry Gardens to a Teahouse...
Plus a link to Wikipedia article on Japanese Tea Ceremony
And, couldn't resist: a youtube link to Tea at Koken; once there, you will find other video-clip offerings of tea ceremonies.