Other names for carom include ajwain and bishop’s weed. The use of carom seeds is mostly limited to India and the state of Gujarat in particular. It is used to flavor vegetarian dishes as well as breads and pastries including roti and paratha. It is also popular for flavoring fried potatoes and is included in some curry powder blends. For the most authentic flavor, you should seek this spice out online or at an Indian grocery store. If that is not an option, consider a carom seed substitute.
Your best bet: Dried thyme
One of the main characteristics of carom seeds is their striking similarity of their flavor to that of thyme but with a slightly musty undertone. That mustiness makes dried thyme the ideal stand-in. Thyme is a member of the mint family and comes in many different variations. The one that works best as an alternative to carom seeds is the standard variety referred to as common thyme.
Both thyme and carom seeds have the same combination of woodsy and minty notes as both are rich in the essential oil thymol. If you use dried thyme as your carom seed substitute, use exactly the same amount that your recipe specifies for carom seeds.
A decent second choice: Mediterranean or Mexican oregano
Like thyme, the most common type of oregano is Mediterranean in origin and a member of the mint family. Its strong, earthy notes and sharpness do a good job of standing in for carom seeds. The aromas are especially similar; as a result, oregano should work well in most dishes that require carom seeds. Mediterranean oregano has the fortitude to withstand longer cooking times and can even work well in breads and pastries. Because of Mediterranean oregano’s characteristic pungency, you may want to use less of it than your recipe requires for carom seeds.
Mexican oregano belongs to the same family as lemon verbena and has a very similar pungent flavor as its Mediterranean namesake. It pairs well with most of the spices that would show up in a recipe that requires carom seeds. It can also be used fresh or dried.
In a pinch: Marjoram
Marjoram has a similar flavor to both thyme and oregano, which makes it perfect as a replacement for carom seeds. It is also a mint and popular for use in Mediterranean dishes, which are two more ways in which it is similar to the substitutes above. If you decide to use marjoram as your substitute, you should remember that it has a relatively mild flavor that may not hold up with a longer cooking time. Other flavors in curries and similar dishes may also overpower it, which means that might not be the best option for those applications. Consider using the same amount of marjoram that your recipe requires for carom seeds and increase if necessary. With baked goods, consider making a test batch and using that to determine the right amount of marjoram to use.
Dried tarragon is considered a good substitute for thyme, which means that it can also be an effective stand-in for carom seeds. You can use it exactly as you would carom seeds. Note that it does have licorice notes that may not work well in all dishes that require carom seeds.
Cumin can also work as a replacement for carom seeds in some applications. Carom seeds do have notes of cumin, which means that you should be able to get a reasonable approximation of the flavor with this substitute.