Place the elderflowers (any stems removed), honey, and lemon zest into a heatproof container.
Heat 250 ml (1 cup) of water to just below boiling. Pour this over the honey elderflower mix and stir to combine. Set aside, covered with a cloth, to steep for at least 30 minutes, preferably a couple of hours.
Once the elderflower has steeped, sieve the honey mixture into a large pitcher or other container. Add the remaining water (1.75 litres / 7 cups) and the lemon juice, and stir to combine.
Serve the elderflower lemonade with lemon slices and additional blossoms to garnish. Extra lemonade can be stored in a sealed container in the refrigerator for a couple of days.
