South east ontario tapping

[Run Forest Run!]

Ok, I'm a beginner.
When does it turn? When the buds appear, get large or when they pop?

To be on the safe side at this 'iffy' time of year, test your sap by heating a bit of it in a saucepan before adding it to your sap pan. If it stinks, it's bad. When that happens, that tree is done. Other trees on your property may still be fine, so test each one when in doubt.