Best Spices for Potato Soup: What Each Does

Potato soup is mild on purpose, so most of its seasoning comes from aromatic vegetables and a few herbs. Two extension recipes show the range. Iowa State’s loaded version keeps it simple with onion, garlic powder, black pepper and cheddar.¹ Illinois Extension goes herbal, with toasted dried rosemary and thyme, lemon juice and fresh parsley.² And if you’re using garlic powder, there’s a good reason to stir it into the broth early.

At a glance

Seasoning	Job in the pot	Notes
Onion	Savory base	In both recipes¹²
Leek	Milder, sweeter onion flavor	A classic partner for potatoes³
Celery	Green, savory note	Rib and leaves, sautéed at the start²
Garlic powder or garlic	Savory depth	Simmered in the broth in the Iowa recipe¹
Thyme and rosemary	Herbal backbone	Dried, toasted, added near the end²
Black pepper	Gentle bite	In both recipes¹²
Parsley	Fresh, slightly bitter finish	Stirred in at the end²
Chives or green onions	Mild onion garnish	At serving¹⁴
Cheddar, bacon	Richness, salt, smoke	Cheese stirred in; bacon as a topping¹

Two baseline recipes

Iowa State’s soup is the simpler one. Cubed potatoes and onion simmer in low-sodium broth with garlic powder and black pepper, then get enriched with nonfat milk and cheddar. Toppings like green onions, bacon, ham and croutons are optional.¹ Illinois Extension starts from leftover mashed potatoes. It sautés onion, celery and carrot in olive oil, simmers them in unsalted chicken broth, and finishes with toasted dried rosemary and thyme, lemon juice and fresh parsley, plus salt and pepper to taste.²

These are the extension services’ recipes, not ours. Check the sources for their amounts.

The core seasonings and what each one does

Onion and leek: the base

Both recipes cook the onion from the start. Iowa simmers it with the potatoes, garlic powder, pepper and broth,¹ and Illinois sautés it with celery and carrot in olive oil before the broth goes in.² Some cooks add onion in stages to layer the flavor. Neither recipe does, and we found no test of it.

Leek tastes mild, sweet and onionlike. It’s used widely in European soups and stews, especially alongside potatoes. You can cook leeks whole as a vegetable, but in soup they’re usually sliced and softened with the other aromatics.

Celery: the second aromatic

The Illinois recipe uses one small rib of celery, leaves and all, minced and sautéed with the onion.² Here it adds a green, savory note. Celery leaves, seed and salt carry the same flavor in other forms. See celery leaves, celery seeds and celery salt.

Garlic: hydrate the powder

Iowa’s recipe simmers garlic powder in the broth.¹ That’s a good fit for the powder. America’s Test Kitchen found that garlic powder stirred dry into mashed potatoes tasted harsh and garlicky but not especially complex,⁵ and recommends hydrating it, because powder straight from the jar hasn’t developed its full flavor.⁶ In a soup, putting the powder into the broth early is an easy way to do that. See garlic powder vs. garlic and too much garlic powder.

Thyme and rosemary: toasted, then stirred in

The Illinois recipe toasts dried rosemary and thyme in a dry skillet until fragrant, then adds them near the end with the lemon juice and parsley.² Thyme brings a sharp, savory note. America’s Test Kitchen treats thyme and rosemary as hearty herbs that hold up to cooking,⁷ so either timing works. Dried herbs are stronger than fresh. The University of Delaware’s conversion is 3/4 to 1 teaspoon dried for 2 to 3 teaspoons fresh.⁸ See cooking with thyme and cooking with rosemary.

Black pepper

Both recipes use black pepper. Iowa simmers it in the broth, and Illinois leaves it to taste at the end.¹² Grinding it fresh is up to you. See black pepper.

Parsley, chives and green onions: the finish

Parsley is a delicate herb, and the LSU AgCenter says to add delicate herbs like parsley and chives in the last minute or two of cooking.⁹ The Illinois recipe stirs in fresh parsley at the end.² Flat-leaved parsley has a stronger flavor than curly. You’ll often hear that dried parsley is weaker than fresh. The University of Delaware’s general rule for herbs runs the other way (dried is stronger),⁸ and we found no parsley-specific measurement.

Chives taste mildly of onion and usually get sprinkled on just before serving. Iowa’s recipe lists sliced green onions among its optional garnishes.¹ See chives and too much parsley.

Cheddar and bacon: not spices, but they season

Iowa’s loaded potato soup stirs in shredded cheddar and offers crumbled bacon and diced ham as toppings.¹ If you’re using either, taste before you add more salt. For a smokier soup, some cooks start by rendering bacon and cooking the onion in its fat. Neither extension recipe does that.

Variations

Loaded: cheddar, bacon, green onions on top, as in the Iowa recipe.¹
Herb-forward and lighter: olive oil, celery, toasted thyme and rosemary, lemon and parsley, as in the Illinois recipe.²
Potato and leek: leeks with the onion or in its place.

“Loaded Potato Soup”, Spend Smart. Eat Smart., Iowa State University Extension and Outreach. spendsmart.extension.iastate.edu · Reference work ↩ ↩² ↩³ ↩⁴ ↩⁵ ↩⁶ ↩⁷ ↩⁸ ↩⁹ ↩¹⁰ ↩¹¹ ↩¹² ↩¹³
“Herb Potato Soup”, University of Illinois Extension. extension.illinois.edu · Reference work ↩ ↩² ↩³ ↩⁴ ↩⁵ ↩⁶ ↩⁷ ↩⁸ ↩⁹ ↩¹⁰ ↩¹¹ ↩¹² ↩¹³
“Leek”, Encyclopaedia Britannica. britannica.com · Reference work ↩
Susan Mahr, “Chives, Allium schoenoprasum”, University of Wisconsin-Madison Division of Extension. hort.extension.wisc.edu · Reference work ↩
“Experiment: Bringing Out the Best in Garlic Powder”, America’s Test Kitchen. americastestkitchen.com · Publication ↩
Carolyn Grillo, “For Great Garlic Bread, Hydrate Your Garlic Powder First”, America’s Test Kitchen, 2021. americastestkitchen.com · Publication ↩
Liz Bomze, “Our Guide to Fresh Herbs”, America’s Test Kitchen, 2019. americastestkitchen.com · Publication ↩
“Using Herbs and Spices”, University of Delaware Cooperative Extension, revised 2025. udel.edu · Reference work ↩ ↩²
“Flavorful Herbs”, LSU AgCenter. lsuagcenter.com · Reference work ↩

Also drawn on

Petroselinum crispum (PROSEA), I.B. Ipor & L.P.A. Oyen, Plant Resources of South-East Asia, via Pl@ntUse. uses.plantnet-project.org

The Best Spices for Potato Soup: Aromatics, Herbs and Toppings That Do the Work