Separate 4 cups of lilac blossoms from their stems, carefully removing any green parts.
Pour 4 cups boiling water over the top of the lilac blossoms and allow the tea to infuse for about 10 minutes. It should be a turquoise color (which will change to pink when lemon juice is added). If it’s not, you can add a few mashed blueberries of blackberries at this step for color, but that’s optional.)
Strain the lilac tea into a saucepan or jam pot. Add the lemon juice, which will adjust color, but it’s also required to balance the sugar in the recipe and help the pectin set, so don’t skip the lemon!
Bring the mixture to a boil and add the powdered pectin, stirring to dissolve. Allow the mixture to boil for 1 minute before adding sugar. (Note: Do not add the sugar at the same time as the pectin, or before the pectin, or the jell will not set.)
Add the sugar, stirring to dissolve (See notes on quantity). Bring the mixture back to a full boil for 1 minute before ladling into jelly jars leaving 1/4 inch headspace.
If canning, process in a water bath canner for 10 minutes. Otherwise, allow the jars to cool completely on the counter before storing in the refrigerator (for up to a month) or the freezer for up to 6 months.