Put the picked flowers in a colander and wash them thoroughly under running water. Put them in an enameled or glass container. Add the lemon and water.
Mash the flowers and pieces of lemon with your hand so they release their aroma. Put it in the fridge, let it sit for 24 hours, while stirring from time to time, and then mash the flowers and lemon pieces once again.
Take them out of the fridge for the water to become at room temperature, while stirring. Take the flowers out, strain the liquid.
Add the sugar and stir until dissolved. Distribute into bottles and boil for 5 min. Leave 1 bottle of it in the fridge to have on hand (it doesn't last more than a week).
Enjoy this aromatic syrup year-round.