In a large stock pot over medium heat, dissolve the sugar in water.
Add the juice of one lemon to keep from discoloring, and bring to a boil.
Remove from heat, add elderflower blossoms to boiled water and let steep for 8-10 hours.
Add the juice from the remaining lemons and oranges for flavor.
Strain through cheesecloth or filter.
Add citric acid or more lemon juice if you are going to water bath can- to strained liquid.
Pour into washed and sterilized bottles or containers. You can keep it in the fridge for 3 months. It can also be frozen in ice cube trays for easy use or water bath canned.
Notes
Use granulated white sugar for a lighter color.
Use fresh flowers for a brighter floral fragrance, however, dried flowers will work as well.
For a thicker syrup, use a 1:2 or 1:1.5 ratio of water to sugar.