Bundesgartenschau is a biannual Federal horticulture show in Germany. It has been in existence since 1951. Every 2 years they switch locations within Germany. So far the event has been held in Hamburg, Koln and Hannover amongst other cities. The logo above was created for the 1975 exhibition in Mannheim.
The DBG website contains photos and information of all the Bundesgatrenschau shows. Highlights include the Hamburg 1973 poster (Man with a slinky as a beard riding a tugboat across a sea of flowers..say what?) and the 1957 show poster designed by Herbert Leupin.