Recognize culinary lemongrass and prepare it for salads, soups and curry paste

The short answer

Culinary lemongrass (Cymbopogon citratus) is a tall, clumping grass with a strong lemon fragrance. In the kitchen, its lower stalk does most of the work. How you cut it depends on whether the lemongrass will be eaten or only used for flavor. For salads and curry paste, slice the tender lower section very thinly so it becomes part of the dish. For soups such as tom yum, a Thai hot and sour soup, bruise larger pieces so they release their aroma, then remove them before serving or tell diners not to eat them.

How to recognize lemongrass

The University of Florida's IFAS Extension describes lemongrass as a large perennial grass that grows in clumps. Its long leaves arch and cascade outward, and the plant has a strong lemon scent. Both the leaves and the stalks are used to flavor food, including soups and beverages.

• A firm, grass-like stalk that grows in a clump rather than as a single shoot
• Long, cascading leaves at the top of the plant
• A distinctly lemony fragrance, especially when the stalk is cut or crushed
• A lower stalk that shades from white to light green, with drier, tougher material toward the top and in the outer layers

These traits are enough to recognize lemongrass sold for cooking. They are not a full botanical key, so if you are trying to identify an unlabeled plant growing outdoors before eating it, confirm its identity with a reliable plant reference first.

Which part of the stalk to use

Cooks generally divide the stalk into two zones. The tender lower section can be sliced finely and eaten. The fibrous upper section and tough outer layers are better suited to infusing flavor and then being removed.

• Trim the root end. The Asian5 restaurant's method cuts off about 1 cm from the base.
• Peel away the tough outer layer. Rosa's Thai recommends this step for every preparation.
• Use the lower, bulbous section for fine slicing or chopping. Asian5 uses roughly the bottom 5 cm, and Rosa's Thai uses the white-to-light-green bottom third for salads.
• Keep the upper stalk for infusion. Asian5 crushes these sections, simmers them in the dish and takes them out afterward.

Eaten or infused: the decision that sets your cut

Before you pick up a knife, decide whether the lemongrass should stay in the finished dish or only flavor it. That choice determines which section you use, how you cut it and whether it comes out at the end.

Use	Stalk section	Cut	Stays in the dish?
Salad	Tender white-to-light-green lower part	Very thin crosswise rings	Yes, eaten raw
Infused soup	Lower or upper stalk	Bruised, then cut into chunks or diagonal pieces	No, removed or set aside by diners
Curry paste	Tender lower part	Thinly sliced, then pounded or blended fine	Yes, ground into the paste

For salads: thin rings from the tender base

Because salad lemongrass is eaten raw, only the most tender part works. Rosa's Thai recommends removing the tough outer layer and slicing thin crosswise rings from the white-to-light-green bottom third of the stalk. Thin rings matter here: cutting across the fibers keeps each piece short and easy to chew, while thicker pieces from higher up the stalk stay woody.

For soups: bruise, infuse and remove

In soups, lemongrass usually works like a bay leaf. For soup, Rosa's Thai cuts the stalk on the diagonal and discards the dry, tough ends. Bruising the pieces first helps release their aroma. Clay Irving's kitchen guide describes bruising as smashing a trimmed, peeled stalk with a mortar and pestle, the flat side of a knife or a mallet.

Pailin of Hot Thai Kitchen offers a clear example in a mushroom tom yum. The bottom halves of two stalks are smashed, cut into chunks and steeped in three cups of stock for three to five minutes, together with galangal (another firm aromatic) and makrut lime leaves. In that recipe, these aromatics are not meant to be eaten. They are removed after infusing, and a cheesecloth bag makes this easier. If you leave them in the pot, tell your guests to set them aside.

For curry paste: slice thin, then grind fine

In curry paste, lemongrass becomes part of what you eat, so it has to be broken down completely. Rosa's Thai advises chopping it before pounding or processing, since whole lengths of stalk won't break down evenly. Pailin's red curry paste uses the bottom half of one stalk, thinly sliced. The slices are pounded with the other firm aromatics until fine, or blended finely with an immersion blender. The lemongrass stays in the paste.

A quick planning worksheet

When following a new recipe, it helps to map each lemongrass step before you start. The illustrative entries below use the two Hot Thai Kitchen recipes described above.

Dish             | Recipe              | Section              | Cut                     | Role         | At the end
Tom yum          | Mushroom tom yum    | Bottom halves        | Smashed, cut in chunks  | Infused      | Remove or warn diners
Red curry paste  | Red curry paste     | Bottom half, 1 stalk | Thin slices, ground fine| Incorporated | Stays in the paste

If a recipe doesn't say whether the lemongrass should be eaten, let the cut guide you. Large bruised pieces are almost always meant to be removed. Fine rings or ground lemongrass are meant to stay in the dish.