In a medium saucepan, bring 1 cup water and sugar to a boil over medium-high heat, stirring occasionally, until sugar is dissolved. Remove from heat, add lavender and blueberries, and let steep for 10 minutes; crush blueberries and steep 10 minutes more.
Strain mixture through a fine-mesh sieve, discarding lavender and blueberries. Refrigerate until completely cool. Store in an airtight container for up to 1 month.
Recipe by Victoria at https://victoriamag.com/limoncello-spritzer-lavender-syrup/