Pick the petals. Remove any spoiled specimens, remaining leaves and stamens. Rinse from in running water and transfer to a saucepan. Place the mint and hibiscus tea. Pour boiling water and leave to infuse for 3 hours.

Boil the contents of the pot. Cool.

Strain the decoction through a colander, squeeze the petals.

Pour in the sugar and citric acid. Boil the syrup until thickened about 12 minutes over medium heat. The syrup is ready when a drop on a cold dish holds its shape and does not spread.

The syrup can be poured into a pitcher and stored in the refrigerator. For longer storage, use sterilized jars with airtight lids.