Make a simple syrup by placing 1 cup of granulated sugar and 2 1/2 cups of water in a small saucepan over medium-high heat. Bring the mixture to a boil while stirring or whisking it frequently. Boil until the sugar is dissolved.
Remove the pot from the heat and stir in the dried lavender, cover, and let it infuse while it cools completely.
Pour the syrup through a strainer to remove the flowers.
Stir the syrup into the remaining 2 1/2 cups of water, and add the lemon juice. Stir to mix.
Serve the lavender lemonade over ice with a slice of lemon and a sprig of fresh lavender for garnish if you have it.