In a small saucepan, bring 1 cup of water to a boil. Once boiling, remove from heat and add the dried culinary lavender. Let it steep for about 15 minutes to create a lavender infusion. Strain and set aside to cool.
While the lavender is steeping, blend the fresh blueberries in a blender until smooth. If desired, strain the blueberry puree through a fine mesh sieve to remove the skins and seeds.
In a large pitcher, mix the cooled lavender infusion, fresh lemon juice, honey or agave syrup, and the blueberry puree. Stir well until all the ingredients are nicely combined.
Pour in the 4 cups of cold water to dilute the mixture. Taste and adjust sweetness or tartness by adding more honey or lemon juice as needed.
Refrigerate the lemonade for at least 1 hour to chill.
When ready to serve, fill glasses with ice cubes, pour the blueberry lavender lemonade over the ice, and garnish with fresh blueberries and a sprig of lavender if desired.
Notes
Adjust sweetness to taste with honey or agave syrup.