Place 4 half pint (8 oz.) mason jars in a large stock pot/canning pot. Add enough water to cover the jars and bring to simmer. Place the lids into a small saucepan and simmer those in a bit of water as well. No need to warm the rings, just the lids. (Make sure you are using new lids, it's best not to reuse them.)

Put a small plate in the freezer to test doneness for jam.

Combine sugar and lavender in a food processor and pulse 20 times or so to break up the flowers. You can also rub them between your fingers with the sugar to break them up. Set aside.

Add blueberries to a large, wide pot and crush with potato masher. Add pectin to crushed blueberries and stir to combine. (You'll want plenty of room at the top when the mixture starts boiling)

Next, add lemon juice to blueberries, stir to combine and bring to a boil, stirring occasionally, then add lavender sugar all at once and stir until completely dissolved. Return to a rolling boil and let it boil HARD for 60 - 90 seconds, stirring constantly.

Reduce heat and let the jam simmer for 20 - 25 minutes until it reaches gel stage. (Test jam by placing a teaspoon on the plate from the freezer. Return to the freezer for 1 minute. Swipe your finger through the jam - if it stays separated, you're done).

Remove from heat and skim off as much foam as you can without taking too much of the jam. *see note

Using canning tongs (or regular tongs with a dish towel wrapped around them) remove the jars from the water, pour the water out and set a wide mouth funnel inside of one jar.

Using a ladle or measuring cup, scoop blueberry lavender jam and pour into warm jar leaving 1/4" of space at the top. Repeat until all the jars are filled, then wipe the rim of the jar with a damp towel, making sure the thread of the jar is clean.

Remove the lids from the simmering water, screw on the rings to "fingertip tight" - do not tighten all the way. Repeat with remaining jars.

Place jars into a canning rack if you have one and lower into water in canning/stock pot. If not, use tongs and lower the jars one by one (fairly quickly) into the water. Make sure water covers the jars by at least an inch, two if possible.

Bring water to a full boil. Boil for 10 - 12 minutes, then remove from water. (I always place my hot jars on top of a dishtowel on the counter so nothing slides around.)

Leave jars for 24 hours, you will hopefully hear that beautiful "PING" sound fairly soon after they've come out of the water, but it may take a little while. To make sure the jar has sealed properly - press on the lid. If it has ANY give whatsoever, that jar has to go in the fridge.