The Ontario Horticultural Association, GardenOntario, maintains a Province wide events Calendar for gardening activities. This can be sorted by Date, District and Society.
Nearby Societies can be found on the District 10 site – Stratford is in District 10 – which covers events in Oxford, Middlesex, Elgin, Perth and Huron Counties.
District 19 offers events in Kitchener-Waterloo and Cambridge. https://gardenontario.org/district-listing/entry/636/
Direct link to OHA main page https://gardenontario.org/
Direct link to Events https://gardenontario.org/events/
Direct link to Garden Shop https://gardenontario.org/gardenshop/