Well I would suggest if you really can not get it, then leave it out altogether.
It provides accents of flavour rather than a primary usually in most curry recipes, so it can be omitted.
If you want to substitute it, then you can use lemon or lime zest, possibly with some mint leaves to freshen it a little.
But the end result will not be the same, just enhanced in a similar fashion to that which lemongrass achieves.
cooking.stackexchange.com/users/3432/Orbling
Western grocery stores generally don't carry lemon grass, you'll need to go to an Asian market.
Many of them will also sell dried (powdered) lemon grass, which is definitively the best substitute you can find for fresh lemon grass.
Honestly, there's really very little else you can substitute.
Lemon grass has this hint of citrus flavour but also, as the name implies, a sort of grassy , herb-like flavour.
If I were really desperate, I would substitute lemon zest (fresh only ), at 1/2 tsp for each lemon grass stalk called for by the recipe, and several pages online seem to suggest adding in some arugula (to give it that grassy quality).
But be warned, it is not going to be the same, it's going to be a great deal more bitter, so consider either reducing the quantity or adding more sweet/savoury spices or ingredients to the curry to compensate (cinnamon, perhaps).
cooking.stackexchange.com/users/41/Aaronut
I always think lemongrass tastes more like lime than lemon.
I'd use the grated zest of a lime, perhaps mixed with some of lemon.
cooking.stackexchange.com/users/4194/ElendilTheTall
Lemongrass freezes well.
If you cannot find it in the fresh section, try the frozen section of the market.
Personally, and unfortunately, I haven't been able to find it even it at my own local Asian market.
Recipes in some of my cookbooks call for lemon zest as an alternative.
cooking.stackexchange.com/users/4226/ewindisch
I'm certainly not an expert but as was mentioned briefly before, lemon balm might be a better substitute than lemon or lime zest.
It has a subtle lemon-y flavor and also the 'grass-y' note (if fresh).
I've used that before when I was out of lemongrass and
it was better than leaving it out.
I just had to play with the amount, however, adding tiny bits at a time and tasting.
cooking.stackexchange.com/users/10766/Tamara Morgan
I have a meal planned in a few days and it calls for lemon grass.  Problem is I've been to the store a couple of times and they don't have it.    (the store is a block away and I don't feel like driving all the way to the next one to look)  The dish is curry spiced noodles, basically a stir-fry.  Any suggestions?
Substitute for lemon grass in curry dish
cooking.stackexchange.com
<substitutions><herbs><curry>
cooking.stackexchange.com/questions/10921
cooking.stackexchange.com/users/3861/ptpaterson
You could use lemon or lime zest, possibly mixed with arrugula for the grassy quality, or use lemon balm instead. The the zest of a lemon or lime or some lemon balm.
Try using the zest of a lemon or lime instead. Try using lemon balm instead.