In a small saucepan, combine 1 cup water, honey (or sugar), and lavender.
Heat over medium heat until the mixture simmers, then remove from heat and let steep for 10 minutes.
Strain out the lavender flowers and let the syrup cool.
Add the blueberries to a large pitcher and gently mash with a muddler.
Pour in the lemon juice, cooled lavender syrup, and remaining water.
Stir well to mix all ingredients.
Add ice cubes to the pitcher or directly to serving glasses.
Garnish with extra blueberries, lemon slices, and a sprig of lavender if desired.