Put lemongrass, lemon verbena, lemon balm, and zest in a heatproof container. Pour 2 cups boiling water over herbs and steep 20 minutes. Strain, then stir in sugar.
Divide liquid between 2 ice-filled glasses. Top each with about 1/2 cup black tea. Garnish with lemon verbena leaves.
*Grow your own lemon verbena and lemon balm, or look for them at a farmers' market.