National Public Gardens Day National Public Gardens Day was created in 2009 to drive local and national exposure to the importance of building vibrant, relevant gardens committed to community enrichment and environmental responsibility through community engagement, sustainable practices, and conversion. The Cincinnati Zoo will join the celebration by hosting a garden celebration on Saturday, May 18. This event is an opportunity for the Cincinnati Zoo to highlight all the imperative work we currently do in the field and do it in a fun and interactive way for all ages! Five engaging and educational stations will be placed among the Zoo gardens for guests to enjoy. ‘ This event is free with Zoo admission.