Basil vs. Parsley: The Lead Herb and the Supporting One

Basil and parsley are both green leaves that finish a dish, but they come from different plant families and carry very different amounts and kinds of aroma. Basil oil is built on methyl chavicol (estragole), a sweet-spicy compound,¹ while parsley’s small amount of leaf oil is led by compounds such as 1,3,8-p-menthatriene, limonene and myristicin, and its flavor runs warm and slightly bitter.² Basil is the flavor of a dish; parsley more often supports one.

Side by side

For other members of each family, oregano is in the mint family with basil, and cilantro is in the parsley family.¹⁰¹¹

How much aroma, and from what

The oil figures below come from different works and are not measured on the same basis, so they show direction rather than a precise ratio.

Britannica gives a much lower figure for basil, 0.1%, also without a stated basis, so the basil oil content itself is disputed.⁵ Even so, the sources agree on the compounds: basil and parsley share no lead compound, and neither tastes like the other.

PROSEA also says flat-leaved parsley is stronger flavored than curly,² the reverse of what the oil-content figures alone might suggest. PROSEA does not explain why.

The differences that change a dish

Role

In our judgment basil leads and parsley supports. A handful of basil defines a pesto or a tomato salad; a handful of parsley brightens a stew, a sauce or a plate of fish without taking it over. Britannica lists parsley with fish, meats, soups, sauces and salads,⁶ and PROSEA notes that curly-leaved parsley is commonly used for garnishing and seasoning.²

Fresh, dried and heat

A widely repeated claim says dried basil is worth using while dried parsley is not. America’s Test Kitchen puts both in the same group of herbs that are much weaker in flavor when dried,⁷ and its tests describe delicate herbs, basil and parsley among them, as more volatile.¹² LSU AgCenter lists both among the delicate herbs best added in the last minute or two of cooking.¹³ For long-simmered dishes, the University of Delaware’s gentler rule is to add herbs during the last 45 minutes.¹⁴ See dried basil vs. fresh and fresh parsley vs. dried.

Which parsley

PROSEA describes three cultivated groups: curly-leaved parsley with compact branches and curled leaf blades, flat-leaved parsley with more open branches and flat leaf blades, and turnip-rooted parsley, a more robust plant with long fern-like leaves.² For cooking, flat-leaved is the stronger-flavored of the leaf types.² See Italian parsley vs. curly parsley.

Can one stand in for the other?

For looks, sometimes; for flavor, rarely. Neither direction has a published ratio, so both are Method.

• Basil in place of parsley. The parsley substitutes page suggests starting with about half the parsley amount and tasting, and keeping basil to Italian dishes where it already belongs. A chiffonade of basil gives a similar green finish, but basil will stand out where parsley would blend in (editorial).
• Parsley in place of basil. Parsley adds color and a fresh, slightly bitter note but none of basil’s sweetness or anise. In a tomato sauce or salad, start with the same amount and accept a different dish; in pesto, a parsley version is a different sauce rather than a stand-in (editorial).

Safety notes

Neither herb is a concern at normal kitchen amounts, but each has one point worth knowing:

• Parsley and warfarin. MedlinePlus lists parsley among foods that can affect warfarin; its advice is not to avoid these foods but to keep amounts small and steady.⁹ Britannica warns that parsley seed oil, or large amounts of other parsley preparations, can cause serious reactions; that concerns concentrated preparations, not leaves in cooking.⁶
• Basil and estragole. Germany’s BfR names basil-containing pesto among foods that may contain high amounts of estragole and related compounds.⁸ The basil profile covers what regulators have concluded.

What isn’t known

• No study compares the flavor strength of basil and parsley, so the swap amounts above are starting points.
• Basil’s essential oil content is reported as about 1.5% by PROSEA and 0.1% by Britannica, neither with a stated basis.¹⁵
• The often-repeated description of flat-leaf parsley leaves as “rosettes” could not be traced to a source.

Related

• Profiles: basil, parsley, cilantro
• Parsley substitutes
• Comparisons: cilantro vs. parsley, oregano vs. parsley, chervil vs. parsley, flat-leaf vs. Italian parsley, basil vs. oregano, basil vs. cilantro
• Cooking with basil, how to store basil, how to store parsley