To make the sugar syrup, combine sugar, water, and orange zest in a medium saucepan. Bring to a boil, stirring to dissolve sugar. Remove from heat and let cool. Pour the syrup through a fine-mesh sieve placed over a bowl, pressing down on the orange zest with a spoon to extract as much of the flavor as possible. Set aside.

In a medium saucepan, bring 4 1/2 c. water to a boil. Add spearmint tea, remove from heat, and let steep for 5 min. Strain tea through a fine mesh sieve placed over a bowl. Let cool.

Place strawberries in a fine-mesh sieve over a bowl. Use the back of a large wooden spoon to press the berries through the sieve, leaving the pulp and seeds behind. Add puree to the tea. Add orange juice and 1/2 c. of the sugar syrup to the tea and stir vigorously. Taste and add more syrup if desired (leftover syrup can be store in the refrigerator for another use). Cover tea and refrigerate until well chilled. Serve over ice in chilled glasses. Garnish with sprigs of fresh mint and sliced strawberries if desired.