Fennel vs. Dill: Two Feathery Herbs With Different Chemistry

Fennel and dill are both feathery herbs of the carrot and parsley family, with leaves alike enough to fool a shopper. Taste them and the main difference is plain: fennel tastes of licorice and dill doesn’t. Their oils are built from different compounds. Fennel’s anise flavor comes from anethole,¹ while dill leaf oil is led by phellandrene and a compound called dill ether.² Fennel is also a vegetable, while dill is only ever an herb and a seed.

Side by side

Two cautions on the compounds row. The fennel figures are for the seed oil, because no source we opened gives a composition for fennel leaf oil. PROSEA says only that the leaves and stems carry less anethole and fenchone than the ripe fruit.¹ And the dill figures are literature values PROSEA summarizes, not measurements of a supermarket bunch.² The flavor row fits the chemistry: PROSEA credits anethole with fennel’s anise smell and sweet taste, and it isn’t among the main compounds PROSEA lists for dill.

For each herb on its own, see dill, fennel seed and bronze fennel, a purple-leaved herb fennel.

The differences that change a dish

Flavor

This is the big one. Both kinds of fennel, the herb and the bulb, taste of anise or licorice. Dill is warm and slightly sharp, somewhat like caraway. In a dish, fennel fronds push a sweet anise note forward. Dill tastes green and fresh, with only a faint anise hint that some people pick up.

Leaf and seed are different products

Both plants give you a leaf and a seed. In dill the two taste different because the oils differ: phellandrene and dill ether in the leaf, carvone and limonene in the seed.² See dill seed vs. dill weed. In fennel, the flavor concentrates in the seed. In mature fennel, about 95% of the oil sits in the fruit.¹

Fennel is also a vegetable

Florence fennel is a group of cultivars grown for the swollen base of the leaf stalks, eaten cooked as a vegetable. That’s the bulb-like stem base of Florence fennel. The bulbs go raw into salads or get steamed, and Florence fennel is shorter, with darker green foliage, than herb fennel. Dill has nothing like it.

Heat and timing

LSU AgCenter lists dill leaves among the delicate herbs to add at the end of cooking, since long heat costs flavor and aroma. We found no comparable guidance for fennel fronds. Cooks tend to treat fronds the same way, while the bulb and seeds can take long cooking.

Can one stand in for the other?

As a garnish, yes. For flavor, only partly, and one direction works better than the other.

• Fennel fronds for fresh dill. A Couple Cooks names fresh fennel fronds the next best substitute for fresh dill: they look just like it and have a subtle licorice finish, though the food writers say dill is hard to replace.³ Ratio (Method): Start with the same amount and taste. See dill substitutes.
• Fresh dill for fennel fronds. We found no source that recommends this. Dill can match the look, but it brings no anise, so the dish loses fennel’s main note. Use it as a garnish, at the same amount.
• Dill seed for fennel seed. The Spice House, a spice merchant, says dill seeds give lasagna a similar texture without the strong licorice or anise flavor, and suggests a small pinch of crushed anise seed to bring some back.⁴ Ratio (Method): Start with an equal amount. See fennel seed substitutes.
• Pickles. Dill is the pickle herb. In the National Center for Home Food Preservation’s tested recipe for quick fresh-pack dill pickles, each pint jar gets 1 1/2 heads of fresh dill or 1 1/2 teaspoons of dill seed.⁵ Fennel would make a different pickle, and in home canning it’s safer to follow a tested recipe as written.

When to use which

• Dill. Pickles above all, including pickled cucumbers and onions. Also fish, soups, salads and sauces. Dill is especially popular in eastern European and Scandinavian cooking. It goes into gravlax, potato salad and sour cream or yogurt sauces too.
• Fennel fronds and herb fennel. The leaves are used as a pot-herb, especially in fish sauces and as a garnish, and in fish dishes, soups and stews. Try tossing a few fronds into a salad.
• Fennel bulb. Raw in salads or steamed. It’s also good braised or roasted.

What isn’t known

• No source we opened gives the composition of fennel leaf oil, so the leaf-to-leaf chemistry comparison has a gap.
• Fennel is often called a classic cioppino ingredient. We found no source for that and left it out.

Related

• Tarragon vs. dill, another anise-tinged herb against dill
• Caraway seeds vs. fennel seeds and fennel seed vs. anise seed
• Fresh dill vs. dried dill, cooking with dill and too much dill
• Fennel pollen and caraway seeds