Collect the blossoms in a place as far as possible from traffic. Put them on a baking tray and let them sit in the sun for a few hours to remove any insects.
Bring water and sugar to the boil. Let it cool down a little, then add lemon slices, citric acid and the blossoms. Cover the pot with plastic wrap (make sure no insects can get to it) and let the syrup steep for 2 days at room temperature.
Remove the blossoms and the lemons. Strain the syrup and bring it to the boil one more time. Pour it into clean bottles while it's still hot.
Tipps
The syrup will last at least a year if the bottles are clean and you pour it into them while still hot. Keep it in a dark and not too warm place. Do you love family recipes? Try this strawberry cake roll – grandma's recipe!