If you don't have fresh lemongrass, here are a few substitutes that will work for lemongrass dressing. For 1 stalk of lemongrass, try 1 teaspoon dry lemongrass or lemon zest (about 1/2 a lemon), ½ a preserved lemon, or 1 tablespoon of lemongrass paste. Lime or orange zest won't be as pungent if you substitute with those.