My property is half an hour north of Cobourg. The flowers are very fragrant. It blooms late Spring through mid to late Summer. It is very old. Was there before I bought the place 30 years ago
Thank you for contacting the Toronto Master Gardeners.
This fragrant deciduous shrub appears to be Philadelphus, more commonly known as mock orange. There are several species. If you would like to learn more about this shrub, here is a link to the Missouri Botanical Garden, where profiles of several types of mock orange can be found: