1 Shake elderflowers to remove any impurities.
2 Rinse orange, lemon and lime and wipe dry. Cut citrus into very thin slices. Layer citrus slices and elderflowers in a large pot.
3 Pour in 2 liters (approximately 8 1/2 cups) of water to cover the fruits and flowers. Place a plate that is slightly smaller than the pot on top of the mixture.
4 Weigh down the plate with 2 large cans. Put pot in the refrigerator and allow to steep for 2 days.
5 Rinse 4 bottles (each 500 ml/approximately 1 pint) with corresponding screw caps with boiling water and leave to drain upside down on a paper towel.
6 Line a fine-mesh sieve with a paper towel and set over a bowl. Strain elderflower liquid through sieve and press solids with a wooden spoon to extract liquid.
7 Take out 200 ml (approximately 3/4 cup) of liquid and pour into a pot. Add sugar and bring to a boil, stirring constantly over medium heat until the sugar has dissolved.
8 Stir in the remaining elderflower liquid and citric acid. Bring mixture back to a boil. Add liquid sweetener to taste.
9 Using a funnel and ladle, fill the prepared bottles with elderflower syrup and seal immediately. Store in refrigerator.