From the Events page of the East Tennessee Plant Swap Website:

Ijams Nature Center Annual Seed Swap

Saturday, 31 January 2015, 1pm – 4pm, at
Ijams Nature Center, Knoxville

Racheff House and Gardens Spring Plant Sale

Saturday, 28 March 2015, 9am – 2pm, at
Racheff House and Gardens, Knoxville

UT Gardens Spring Spectacular Plant Sale

Saturday, 11 April 2015, 9am – 2pm, at
UT Gardens, Knoxville

51st Annual Talahi Plant Sale

Saturday, 11 April 2015, 9am – 2pm, at
Lakeshore Park, Knoxville

Franklin Square Spring Garden Festival

Date and time TBA, at
Franklin Square, Knoxville

Ijams Nature Center Spring Plant Sale

Saturday, 18 April 2015, 9am – 3pm, at
Ijams Nature Center, Knoxville

The Garden Conservancy's Open Day Program

Saturday, 2 May 2015, time may vary by location, at
various private gardens in and around Knoxville

UT Gardens Blooms Days

Saturday and Sunday, 9 & 10 May 2015, starts at 9am, at
UT Gardens, Knoxville

Spring 2015 East Tennessee Plant Swap

Saturday, 16 May 2015, 9:30am – 1pm, at
New Harvest Park in Knoxville