Now that you all have had ago with elderflower cordial..something else to try..
1 kg rhubarb...rinsed and chopped up into small pieces
1 lemon...washed and sliced
500 ml caster sugar (liquid measurement)
1 tablespoon of citric acid
2 litres of boiling water
spring of lemon balm or lemon verbena...optional
All incredients into large pan..pour boiling water over and stir..
Let it stand under lid or towel for 12-24 hrs..sieve and bottle..
Dilute to taste..

Now I have done this and added some left over jam to finish the jar up..and it did gave nice fruity flavour..stawberry jam goes well with rhubarb ..

And best thing about this is as rhubarb start going off season and not so nice anymore for eating..you can still use it for this recipe..