September 11 + 12: Lakeshore African Violet Society Show and Sale. Chicago Botanic Garden, 10am to 4:30pm.
September 11 + 12: Gethsemane Garden Center Annual Sidewalk Sale - This is a great time to get pottery, out-of-flower orchids, and more on the cheap. Between you and me, they have tradescantia, ferns, cyperus, breynias, and many other indoor-friendly plants marked for sale as outdoor annuals. Time to stock up! 9-6pm.
September 18: Hawthorne Garden's Houseplant Seminar. Acclimatizing your pre-existing plants, and adding new ones. 10am.
October 3: Lurie Garden Workshop, "Garden Blogging: Porting Your Garden Journal to the Digital Age." Lecture by Mr. Brown Thumb, hosted in the 1st floor Garland Room, 10am to 12pm.
October 9 + 10: Illinois Orchid Society Show and Sale. Chicago Botanic Garden, time TBA
October 20: Sprout Home's Terrarium Building Class. Registration required (firstname.lastname@example.org), cost approximately $35-$75, depending on selected materials. 6pm.
Everyone's invited over to my place before these events for pregaming, BYOB