Step 1
Inspect 4 small canning jars for cracks and rings for rust discarding any defective ones. Immerse in simmering water until jam is ready. Wash new unused lids and rings in warm soapy water.
Step 2
Combine 1/2 cup sugar and lavender blossoms in the bowl of a food processor; pulse until lavender blossoms are finely chopped and sugar has a light lavender fragrance. Mix fragrant sugar and cherry juice together in a bowl and stir to dissolve. Strain out larger lavender bits through a fine sieve into a large pot. Stir in pectin.
Step 3
Slowly bring cherry juice mixture to a full rolling boil over medium-high heat that does not stop bubbling when stirred. Stir in remaining sugar and return to full rolling boil. Boil for exactly 1 minute stirring constantly. Remove from heat. Skim off any foam with metal spoon.
Step 4
Ladle jelly immediately into prepared jars and add a small lavender sprig to each glass filling to within 1/4 inch of the top. Run a clean knife or thin spatula around the insides of the jars to remove any air bubbles. Wipe rims with a moist paper towel to remove any spills. Top with lids and tightly screw on rings.
Step 5
Place a rack in the bottom of a large stockpot and fill halfway with water. Bring to a boil and lower jars 2 inches apart into the boiling water using a holder. Pour in more boiling water to cover jars by at least 1 inch. Bring to a rolling boil cover and process for 10 minutes.
Step 6
Remove the jars from the stockpot and place onto a cloth-covered or wood surface several inches apart. Let rest for 24 hours without moving the jars. Gently press the center of each lid with a finger to ensure the lid does not move up or down. Remove the rings for storage and store in a cool dark area.