Place lavender buds in a 2-cup glass measuring cup. Add 1 cup boiling water to measuring cup. Cover; let steep for 5 minutes. Pour mixture through a fine mesh strainer into a 2-quart pitcher; discard lavender buds.
Stir lemonade into mixture in pitcher. Cover; chill several hours.
To serve, pour lemonade mixture over ice cubes in stemmed goblets. Garnish each with a lemon slice and fresh sprig of lavender, if you like. Makes 8 (about 7-ounce) servings.