I messed about with this a LOT last year, changing it slightly & experimenting with the quantities.
What works for me (and was eventually agreed by EHO so I could sell it
) is;
Pick the nettles (top 4-6 inches) and rinse them in cold water.
Mix boiling water with sugar and citric acid and stir til it dissolves, then add the washed tops.
Weigh down the nettles in the syrup (I use a big, heavy plate) and stir every day for 5 days.
After 5 days, strain the mixture and bottle.
I use sterilised bottles, filled when hot. Then I place the lids on loosely and put in a water bath, bring the temp to 75C and hold there for 10 minutes before sealing the bottles. I find it keeps for 6 months easily, but don't have any older than that to test (it always sold out
)
I think it has a lovely berry flavour, with a bit of 'greeness' to it - it is really nice (even the kids drink it) and it's lovely if you add a dash to a white wine spritzer