The wait for ripened blueberries usually extends into the final months of summer here in NL. It varies each year depending on the overall climate of the season. Personally, I can recall picking blueberries as early as July with my childhood friends. However I also have fond memories of filling up my grandparents buckets with blueberries every labor day weekend when they would collect their supply for the year.
Being in a boreal forest, these are not the only berries that are inherent to the island. There are seasons for picking blackberries, partridgeberries, cranberries, and even crackerberries. The link below expands on one particular Newfoundland trail that outlines an approximate schedule for local and visiting berry pickers alike. Enjoy!