Yeah sorta it's unique.
Hmmm let me think it make you think lemon but it's also got a herbal almost sweetness to it maybe it's that eucalyptus thing maybe it can taste sometimes slightly medicinal as well
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I rekon lemon grass would be closer lets put it that way.
I've tried kafir lime leaves 2 in one in place of the myrtle leaves and they didn't do the job.
But after all that waffling yup
@RoadRoach is on the money nothing wrong with lemon zest I'd use the juice as well it'll provide some Ascorbic Acid which will help with oxidation.
My original ginger beers back a few years ago were cinnamon stick and one or two lemons along with the ginger.
Think ginger lemon honey tea you know the ones you sip on when your crook.
Some Aussies won't like the lemon Myrtle because we have dishwashing liquid sented with it here so it can remind you of dishwashing residue but well that's an individual preference thing...