Some well-stocked grocery stores may have lemongrass. Or you can usually find it in the produce section of Asian markets. It’s typically sold in bundles of 2 to 3 stalks. Choose ones that have fresh-looking bulb ends and tightly wrapped leaves.
Wrap stalks well in paper towels, then place in a plastic bag (to keep them dry). Lemongrass will keep in the fridge for 2 to 3 weeks.
The citrusy flavor of lemongrass is concentrated in the bottom 5 inches of the stalks, under the layers of dry, papery leaves. To get to the good stuff, cut off and discard the top green portion of the stalk and peel off the leaves. Trim the bulb end, then finely chop the rest of the stalk to use in curries or stir-fries. Or leave the piece whole, bash it lightly with the dull side of a large knife to release the flavor, and use it to infuse soups or sauces. Discard the stalk before serving.