Peel a whole lemon.
Combine the water and the sugar in a large saucepan over medium heat.
Stir occasionally until the sugar dissolves.
Add the hibiscus flowers and the lemon peel, turn the heat high and bring to a boil.
If you want your syrup very thick (grenadine-like), leave the mixture boiling for about 10-15 minutes before removing it from the stove. If you want it less dense, remove it from heat immediately after the boil, and steep it for 20 minutes.
Let the mixture cool down.
Strain it through a fine sieve to discard the hibiscus flower leftovers.
Bottle and label. Syrup will be good for up to 3 weeks when refrigerated.