Aromatic vegetables are essential ingredients in making great soup. Learn all about aromatics in this first part of my ultimate soup guide.
What are Aromatic Vegetables?
Aromatics are a group of vegetables that impart deep, rich flavors to a recipe when sliced, chopped, or crushed and then cooked.
In soup, aromatics serve as the foundational layer of flavors: they’re usually the first or second (if you’re browning meat) ingredient group that goes into the pot: they’re sauteed in oil or butter or broth and the flavors they release add dimension and character to the soup.
When we think “aromatics,” usually onions and celery spring to mind, but the group of aromatics is actually much large than that.
In this article, I’ll cover the long list of aromatics available to cooks, including the classic blends, and how to use them in soup recipes.
Note that the term aromatics also includes aromatic herbs and spices, which will be covered in a separate section. Today we’re focusing on vegetables!
For the more unusual aromatics, I’ll provide links to my recipes where I’ve used them, so you can see them in action!
I’m going to invent two cooking terms here, just for the purposes of this soup guide. I don’t use these terms in my recipes, but for educational clarity, I think they’ll help new cooks and new soup-makers more easily understand when to add certain ingredients to the pot.
Stage 1 Saute: stage one will refer to the first set of aromatic vegetables added to the soup pot to saute in fat or broth. These vegetables take longer to cook and soften and can tolerate the direct heat of hot oil or butter in a pan without burning. Onions, peppers, celery, carrots, and leeks, for example, are all Stage 1 aromatics.
Stage 2 Saute: stage two will refer to the second group of aromatics (or other flavoring ingredients) added to the pot after the Stage 1 ingredients have cooked as instructed but before broth or stock is added. These ingredients — such as garlic, ginger, and shallots — are often tender and heat-sensitive and would burn if forced to cook as long as Stage 1 ingredients.
Other Stage 2 ingredients, such as tomato paste (discussed in a later lesson), would interfere with the saute process if added during Stage 1, but still benefit from a short stint of direct heat to bloom their flavors. Or in the case of herbs and spices, they’ll better release their flavors if sauteed for a shorter stretch.
An example of a two-stage saute would be first cooking onions, carrots, and celery in olive oil for 8 minutes to soften (Stage 1), and then stirring in garlic and ginger (Stage 2) for just a minute until fragrant, before continuing with the recipe.
My recipe for Cold-Fighting Couscous Chicken Soup is a great example of a two-stage saute in action: in the recipe card, read through step 1 under Stovetop Directions.
Again, these are made-up-by-me terms and are not cooking industry recognized! I’ll identify each aromatic below as Stage 1 or Stage 2.
The Onion Family
Probably the best-known and most used aromatic, the onion family includes a lovely assortment of options that can be used individually or together.
Note that the onion family is actually quite large, but I’ll only be covering the vegetables commonly used as soup aromatics here. Other members, such as chives and scallions, are used more as garnishes for soups because their milder flavors and more tender constructions don’t always hold up well to cooking.
These are the standard globe onions found in the produce section at the grocery store and include red onions, yellow onions, white onions, sweet onions, plus specialty varieties such as Walla Walla and Vidalia.
Onions are the core of the typical aromatic base and are usually used diced or sliced thinly into half or quarter moons. They are Stage 1 Saute aromatics and almost always are the first vegetables to go into the soup pot.
Whole onions (sometimes sliced in half) are typically used in making homemade soup stocks and broths, where their solids will be strained out (with all of the other ingredients) after cooking.
Onions come in a wide variety of sizes — even within the same crop — so recipes sometimes call for a vague amount of onions: a “1/2 of an onion” or so. When sufficiently sauteed and softened at the start of the cook, most soups can accommodate quite a large quantity of onions, so in most cases, you don’t need to worry about being precise. (Learn how to prepare onions.)
The leek is a type of onion that grows in a long, slender stalk, rather than a bulb. Mild and lovely and ever so slightly sweet, they go particularly well in soups and pair wonderfully with other onions. The dark green leaves — known as “flags” — are generally not consumed in soups because they’re quite tough, but are wonderful ingredients for making soup stocks.
Leeks consist of concentric rings of flavorful layers (visible in the photo above), each ring being nourished by its own flag. Because of the plant’s open structure, dirt can easily slide down the flags into the rings. So, leeks need to be cleaned carefully before use. (Learn how to clean leeks.)
Unlike onions, leeks need to be refrigerated and are usually found on the refrigerated produce wall or case at the store. Sometimes they’re trimmed of their flags and roots; sometimes not. If you’re lucky, your store sells them individually.
Puzzlingly, my Kroger sells them in bundles. They’re not only quite large — hello, normal-sized refrigerator — but even as a leek aficionado, I’m hard-pressed to use up 3 or 4 leeks several days in a row.
Leeks are Stage 1 Saute aromatics and are cooked with onions, carrots, peppers, etc., early in the soup recipe.
Soup recipes using leeks:
Shallots are another member of the onion family. Botanically, they’re super interesting, in that they grow underground like bulb onions, but in big clusters that come out of the ground in a gnarly bunch. So, one plant will produce a cluster of three or more shallot bulbs.
They’re also often cloved, like their cousin, garlic: one papery-wrapped bulb can contain two distinct cloves within. At the store, you can usually feel or see the separate cloves, as there will be irregular humps on the bulb rather than a uniform round or oval appearance (as with a bulb onion).
The presence or absence of multiple cloves does not indicate quality — it’s just how they grow. You never know what you’re going to get!
Flavor-wise, for such a little bulb, they pack quite a punch! They’re more pungent than bulb onions, with just a hint of garlic. They’re also a bit tender and they cook up much faster than onions, making them a Stage 2 Saute vegetable.
To prep, treat them like onions: cut off the stem end, peel away the papery outer layer, and slice or dice the layers inside.
Because of their distinct flavor, shallots are often used in sauces (such as classic Hollandaise) and raw in salad dressings.
Soup & Stew recipes using shallots:
Celery is a lovely, crunchy vegetable that’s actually related to carrots, fennel, and cilantro. Its astringent flavor profile is always welcome in soups, as it balances the more potent notes of onions and the sweetness of carrots.
Like onions, celery crosses many cultural cuisines and is an appropriate flavor fit for most types of soups. It’s also part of a few classic aromatic mixes, including mirepoix (see below).
Structurally, celery grows above ground in a multi-branched plant with small green leaves. All of it is edible. The terminology used to identify the various parts of the plant can be confusing. Botanically:
- The whole harvested plant is called a “head” of celery, or interchangeably, a “stalk” of celery. This includes the individual branches of the plant and its leaves. Whole heads of celery are commonly and economically found at the grocery store. Sometimes, the leaves will have been trimmed away.
- The individual branches of celery are called “sticks” or “ribs.” If you think of the peanut butter stuffed celery stick appetizer: that’s a rib. Some recipe developers, however, incorrectly refer to ribs as stalks. With the two hundred or so soup recipes I have on this site, I’m sure I’ve done it, too!
So keep in mind that if you see a recipe calling for 1 or 2 stalks, it’s a good assumption that it means ribs. A head of celery is a lot of celery!
Celery is a Stage 1 Saute aromatic and should be added at the same time as onions. Celery softens quite nicely during cooking, so rest assured that celery will recede nicely into the background of the soup.
Carrots are one of the most popular aromatics for soups and stews, and are one of the key ingredients in mirepoix (see below).
Carrots are both astringent and sweet, and nicely balance the sharper flavors of celery and onions. You can use carrots in both the aromatic saute and as a crunchy soup garnish when grated or shaved.
Note that the dense and somewhat dry structure of carrots means that they take longer to soften during a saute — they are definitely Stage 1 Saute vegetables.
For soup, unless they’re playing a bulk role texture-wise — such as big disks in a stew — dice them small to help with timing, compared to onions and celery. Sometimes I even grate them when I want to ensure that the carrots will be very soft in a soup.
For an earthier take on carrots, try their relative, the parsnip. Parsnips look like large, white carrots and can be found on the refrigerated wall of the produce section. Parsnips are particularly lovely in stews, as they’re savorier than carrots but still have a slightly sweet quality to them.
Sweet Bell Peppers
Bell peppers are in the nightshade family, related to tomatoes and potatoes. Bell peppers have no spicy heat, and are named because they have a blocky appearance with a distinct seed pod hanging in the center of the pepper (unlike other many peppers who seeds are often distributed along the ribs).
Although there are numerous cultivars of sweet bell peppers, they all follow the same basic flavor and coloring patterns:
Green — at the green stage, the pepper is unripe, although completely edible. Green bell peppers have a sharp, astringent flavor, compared to their riper stages. Note that for fresh eating, such as on a crudite platter, green bells are not really a 1:1 substitute for red bells. In fact, some people do not like the flavor of green bell peppers at all.
In soups, however, their astringency is quite nice in dishes like chili and gumbo, and green peppers are part of the classic cajun aromatic blend (see below).
Yellow or Orange — There are cultivars of bell peppers that are fully ripe at either yellow or orange. These peppers are sweeter than green peppers, but generally weaker in pepper flavors than red.
Some red bell peppers ripen from green to yellow to red, so as a gardener, yellow or orange is a stepping stone on the way to ripe. Again, bell peppers are edible at all stages; they simply get sweeter when fully ripe.
At the grocery store, you can assume that yellow and orange bell peppers are fully ripe and at their maximum flavor.
Red — Red bell peppers are the sweetest of the bunch and are great both in soups and for fresh eating.
All bell peppers are Stage 1 Saute aromatics. Red, orange, and yellow bells can be used interchangeably in soup recipes.
Botanically, garlic is actually a member of the onion family, but its role in cooking is so significant that it deserves to stand on its own.
While grocery store garlic is, unfortunately, one-dimensional in flavor — because the cultivars used are bred for shipping survival, not taste — if you shop the farmers’ markets instead, you might just find one of the many beautiful varieties grown for cooking.
Chesnok Red, Music, Georgia Crystal, Spanish Roja — and so many more — are full of intensely sensational garlic flavors. They’re worth seeking out if you’re creating a garlic-focused recipe.
In soup-making, garlic is a Stage 2 Saute aromatic, as it’s fairly tender and burns easily. The rule of thumb is to saute garlic until you can smell it, which is just a minute or two.
What about jarred garlic or garlic paste?
Garlic aficionados can be a bit snobby about garlic, and sometimes rake people over the coals in the forums about using processed versions. And I get it. I’ve grown gourmet garlic in my home vegetable garden for 15 years and, as I mentioned above, there’s a huge difference between grocery store and homegrown garlic.
Jarred and tubed paste garlics are … not exactly at their best garlicky goodness. HOWEVER. For soup-making, these options are absolutely fine. If buying jarred or tubed garlic is the only way you’ll get garlic into your soups, then buy the processed garlic! You have my blessing, lol.
There’s nothing that fries my noodle more than food snobbery. There is a laundry list of legit reasons why a cook might need — or simply want — to take shortcuts. I am both a home cooking advocate and a vegetable gardening advocate, and I take shortcuts.
Just be aware that jarred garlic is usually more potent than fresh, so take care if your intent is to spread it on a toasted baguette, or stir it raw in your homemade salad dressing. But the cooking process in soup-making will temper the aggressive notes and everything will be just fine.
If a recipe calls for garlic cloves and you need to substitute jarred or paste, figure about 1 teaspoon per minced clove.
An exception would be something like the somewhat-famous 40 garlic clove soup. Adding 40 teaspoons of jarred garlic is not going to get you where you want to go. Buy the bulbs. 😉
Ohhh, ginger. You are my spicy love. I simply adore ginger.
Ginger is a rhizome that grows underground, with a beautiful leafy green, fern-like canopy above ground that nourishes everything.
At the grocery store, fresh ginger is sold in “hands.” That is, massive clumps of harvested rhizomes are broken into smaller pieces that look like hands with fingers, as seen in the photo above.
The tan outer skin of ginger should be removed, as it has an unpleasant, papery texture. Around the interwebs, you’ll hear folks say to use the edge of a spoon to scrape off the skin, but IMO, a paring knife works much, much better: break the ginger into smaller pieces (i.e., break off a finger) and just slice off the skin in thin strips.
Some of the yellow ginger flesh will go with it, but that’s okay. Ginger is knobby and bumpy and twisty and trying to drag a spoon over these crevices is more aggravation than it’s worth (see same photo above with the crumbs of skin scraped by the spoon that I quickly lost interest in).
In soup, ginger is most often used minced. Peel the ginger and then use a fine grater or micro-planer to produce a small mince. Ginger is a Stage 2 Saute aromatic.
Note also that most grocery stores carry tubed ginger paste in the produce section. I always have a tube of paste in my fridge, because fresh ginger goes out of stock frequently at my local Kroger.
Soup recipes using ginger:
Lemongrass is an unexpectedly beautiful plant, given the rather plain stalks that you find in American grocery stores. This large plant with a leafy, umbrella, fern-like growth habit is native to Asian climates and is most commonly used in aromatherapy.
It is, however, perfectly edible and completely lovely, and pairs perfectly with ginger to create complex flavors within a soup.
The edible stalk grows beneath the soil and consists of concentric layers, much like a leek. The outer layers harden into thick sheets fairly quickly, but the inner layers are tender.
Lemongrass is lemony (of course!), slightly grassy, and sweetly citrusy with just a hint of ginger.
Lemongrass can be used in two ways:
- Use the stalk whole, sliced into shorter lengths to fit the pot (they can be quite long), simmered in the soup, and removed before serving (as you would a bay leaf). This imparts a light background flavor and is appropriate for long-simmering brothy soups.
- Remove the hard outer layers and chop or mince the tender inner layers. Add them to the 2nd Stage Saute (the same as garlic or ginger).
Depending on the region where you live, fresh lemongrass can be difficult to find (it is for me). A completely acceptable substitute, however, is lemongrass paste. Many American groceries carry a brand that comes in a tube and is usually kept in the refrigerated produce section.
I use almost exclusively tubed lemongrass paste. The paste can be substituted 1:1 in any recipe calling for chopped or minced lemongrass.
Another problem with “fresh” lemongrass in America is that by the time they reach grocery store shelves, the stalks are often … not so fresh. Lemongrass stalks easily become quite woody, and require peeling off — and wasting — most of the outer layers. If you’re patient, you could use a mortar and pestle to pound the layers down into a tender paste. That’s asking a lot of the average meal prep, though!
Jarred versions are also available at some stores, but do check the ingredient labels: some contain fish sauce! While fish sauce is an amazing umami ingredient, (1) personally, I don’t feel that lemongrass needs the boost of fish sauce, and (2) lemongrass is, of course, naturally vegan, but the addition of fish sauce means that any soups you intend to be vegetarian or vegan will automatically not be.
Do not use lemongrass essential oils, as most of those products were not developed for cooking.
Soup recipes using lemongrass:
- Instant Pot Carrot Lemongrass Soup
- Lemongrass Curry Soup with Cashew Cream
- Thai Pumpkin Soup
- Cold-Fighting Couscous Chicken Soup
Tomatoes are probably the most versatile, multi-roled ingredients used in soup-making, as they are used, in various forms, throughout the cook (e.g., as tomato paste, as sauce, or diced).
Tomatoes are also aromatics. When added early in a soup, they impart their wonderfully complex mix of acid and sweetness.
Generally speaking, tomatoes are Stage 2 saute aromatics for soup, but Stage 1 for sauces. In most soup recipes, tomatoes are added after onions and friends have softened, but do defer to the recipe you’re using.
This classic aromatic blend is the foundational layer of many soups. Consisting of basically equal parts of onions, celery, and carrots, this mix adds pungency (from onions), astrigent notes (from the celery) and an earthy sweetness (from the carrots).
It’s a versatile mix that can be used reliably as the starter aromatics for most soups and stews. Mirepoix is a Stage 1 Saute blend.
Cajun Holy Trinity
This lovely combo of onions, celery, and green peppers has its roots in the South, where it’s the start of the region’s most delicious dishes, including jambalaya, etoufee, and gumbo.
The Cajun Holy Trinity is a Stage 1 Saute aromatic blend.
Sofrito is a Latin-inspired blend that has many variations around the world, from Puerto Rico and Latin America to Spain, Portugal, and Italy. My version here uses onions, garlic, bell peppers, and tomatoes.
Technically, sofrito is meant to be cooked down with fresh herbs into a saucy mixture and then used to flavor rice, potato, and chicken recipes (and more). But you can also start with this fresh vegetable blend as a Stage 1 Saute for soups.
I hope this section on Aromatics has been helpful. If you have any questions, please leave them in the comments below — I’m notified of new comments! — so that everyone can benefit.
Up next: Umami!
Other posts in the Ultimate Soup Guide Series:
Monday 16th of January 2023
Thanks for all the info. While I've been a home cook for over 50 years I always like hints and explanations to improve my cooking - especially soups. I look forward to the rest of the series.
Monday 16th of January 2023
Thanks, Linda! I agree, there's always something new to learn in cooking - that's one of the reasons I love it so much!