Parsley and dill

Two herbs from one family

Parsley, Petroselinum crispum, and dill, Anethum graveolens, belong to the Apiaceae, the carrot family, which also holds celery, coriander, fennel and caraway. The family makes finely divided leaves, flowers in flat umbrella-like heads called umbels, and aromatic oils in nearly every part, and many of its members are grown for the leaf, the root or the seed. Parsley and dill sit side by side in the kitchens of Central and Eastern Europe, where cooks strew both over soups, potatoes, salads and sauces.

They look different and behave differently. Parsley is a biennial that grows a rosette of dark green, three-times-divided leaves 10 to 25 centimetres long on a taproot in its first year, and only in the second year sends up a flowering stem as tall as 75 centimetres with yellow-green flowers. Dill is an annual, with feathery blue-green foliage on a stem from half a metre to 1.5 metres tall and flat yellow umbels that ripen into seeds 4 to 5 millimetres long. The word "dill" on a pickle jar can mean the leaf, the flower head or the seed, and the three are not the same ingredient.

Parsley: a Mediterranean herb that became a garnish

Parsley's home is the Mediterranean basin: Greece, the Balkans, Algeria and Morocco are its native range. It began as a cultivated plant on the Mediterranean coast in the late third century BCE, where it was grown for decoration and seasoning. The name comes from the Greek petroselinon, rock-celery. Horticultural books say parsley reached England in 1548, but literary evidence suggests it was in use there as early as the Anglo-Saxon period.

Three forms matter in the kitchen. Curly or moss-curled parsley, called French in some books, has tightly crimped leaves and is the one used as a garnish on a plate. Flat-leaf parsley, called Italian, is preferred for cooking by chefs and many gardeners and is described as the more flavourful, though whether it is actually stronger is disputed. The third form is Hamburg or turnip-rooted parsley, grown for its thick white root, which is common in the soups and stews of central and eastern Europe.

Parsley's cooking is often a matter of quantity. In tabbouleh, the Levantine salad, and in ghormeh sabzi, the Iranian herb stew, it is the main substance of the dish and not a trimming. Parsley is a component of the Brazilian seasoning cheiro-verde, and a sprig of it has a place on the Passover Seder plate. In most of the rest of the world it is a finishing herb, added at the end for a clean, grassy note.

Dill: an old herb of the Near East and Europe

Dill has been known since antiquity. A food science paper describes it as wild in the Mediterranean region, where it was known to the ancient Greeks and Romans. The genus name Anethum is the Latin form of a Greek word that meant both dill and anise, and the origin of the English word dill is unknown.

Where dill began is not agreed. One account puts its native range in North Africa, Iran and the Arabian Peninsula, while another describes it as native to southern Europe and western Asia. The two descriptions overlap around the eastern Mediterranean and western Asia.

From there dill went north and east. It is now a staple herb across Central and Eastern Europe, alongside chives and parsley. In Poland a dill and sour cream sauce dresses mizeria, a cucumber salad; in Bulgaria it goes into tarator, a cold yoghurt soup; in Sweden it flavours gravlax, herring and the boiled crayfish of late summer, where the flower heads are called krondill; in Iran it scents shevid polo, a rice dish; and in China it fills dumplings and buns, baozi and jiaozi. Leaves flavour borscht, soups, fish and, above all, pickles.

What gives them their flavour

Both herbs get their character from essential oils held in the leaf, and in neither case is the oil constant. In a field trial in western Turkey parsley oil content peaked at about 0.7 per cent, and the proportion of the oil that is apiol rose from 26 per cent at the first cutting in May to 44 per cent by September, while myristicin ran between 10 and 21 per cent. Early in the season the oil is dominated by a lighter hydrocarbon, beta-phellandrene, and later the heavier phenylpropanoids, apiol and myristicin, take over. The make-up of the oil, and with it the flavour, changes through the season, and apiol is what the plant lays down as it matures. The oil content was highest at the second cutting, in early July, and had fallen to about 0.4 per cent by September, when the leaf yield was greatest; four cuttings between May and September gave 55 volatile compounds in all.

Dill leaf is a much weaker source of oil than dill seed. Reported oil content is as low as 0.08 to 0.3 per cent in leaves, 1.1 to 3.2 per cent in flowers, and 3.2 to nearly 5 per cent in ripe seed. The oils also differ in kind. Seed oil is dominated by carvone, which smells of caraway and spearmint, at about 46 to 50 per cent in a Serbian trial, with limonene, a citrus-smelling hydrocarbon, at 38 to 44 per cent; across countries, carvone has been reported anywhere from 34 per cent in Algerian seed to 75 per cent in Romanian. Leaf oil leans to alpha-phellandrene, which made up 62.7 per cent of the leaf oil in dill leaf oil, and dill oil is also listed with apiole, dillapiole and myristicin. As the plant matures the oil in the green parts falls and the carvone share rises. A recipe that asks for "dill" without saying which part it means can therefore give different results depending on the answer.

What they do in fermented food

Neither herb feeds a ferment. The sugar that lactic acid bacteria turn into acid in a jar of cucumbers comes from the cucumbers, and the herb is there for flavour. Dill is the eponymous ingredient of dill pickles. The US National Center for Home Food Preservation gives a salt-fermented version per gallon of container: 4 pounds of 4-inch pickling cucumbers, 2 tablespoons of dill seed or 4 to 5 heads of fresh or dry dill weed, half a cup of salt dissolved with a quarter cup of 5 per cent vinegar in 8 cups of water. Half of the dill goes on the bottom of the container and half on top, the brine is poured over, and the container is covered and weighted. It ferments at 70 to 75 °F (21 to 24 °C) for about three to four weeks, in 5 to 6 weeks if kept at 55 to 65 °F, and warmth above 80 °F makes the pickles soft. The recipe lists dill as an ingredient and does not describe its function.

Dill seed oil has antibacterial activity in the laboratory. In disk tests with 10 microlitres of seed oil, the largest clear zone was against Escherichia coli, 15 to 18 millimetres wide; Bacillus subtilis and Proteus vulgaris gave zones of about 11 to 12 millimetres, Klebsiella pneumoniae 11 to 13, and there was no activity against Staphylococcus aureus or Candida albicans. The activity against E. coli was attributed to carvone. These were extracted oils tested alone. A pickle jar holds a few heads or a spoonful of seed in several litres of brine, and the oil content of the leaf is a fraction of that of the seed. Whether dill alters the course of a cucumber ferment is not established. Dill is a flavour, not a starter or a preservative, and a recipe should not rely on it as one.

Choosing and keeping them

Choose bright green, fresh-looking bunches. Parsley that has overwintered runs to seed in its second year and its leaves become tough and bitter, which is why gardeners start new plants each year. To keep parsley, wash the leaves, let them drip dry, put them in a plastic bag and refrigerate. The same treatment suits dill leaf, which wilts quickly.

Both herbs are better fresh. Dill in particular loses its flavour rapidly when dried; dried leaf is sold as dill weed, and freeze-dried leaf keeps its flavour relatively well for a few months. Dill seed is the more stable form: harvest the heads two to three weeks after the flowers appear, hang them in a paper bag in a cool, dry, airy place, let the seeds fall, and store them in a sealed container.

Parsley is rich in vitamins K and C: 100 grams of raw parsley holds about 1,640 micrograms of vitamin K, 133 milligrams of vitamin C, 152 micrograms of folate and 6.2 milligrams of iron, for only 36 kilocalories. Eating it in food amounts is considered safe. Very large quantities may have an effect on the uterus, so pregnant women are advised against eating excessive amounts, and parsley seeds, which carry high levels of apiol, are best avoided.

Growing them

Parsley grows best in moist, well-drained soil in full sun, at temperatures from 22 to 30 °C, though it will take partial shade outdoors. The seed is slow to germinate, four to six weeks, partly because the seed coat carries furanocoumarins, and soaking it in water overnight helps. Leaf parsley is spaced about 10 centimetres apart and root parsley 20. Leaves can be cut any time after the plant is large enough.

Dill wants full sun and moist, well-drained soil, and it grows best where summers are warm to hot; partial shade reduces the yield substantially. Because of its taproot it does not transplant well, so it is sown directly in spring, one to two weeks before the last frost, and sown again every two weeks for a steady supply of leaf. Plants decline soon after flowering. The variety Fernleaf is slow to go to seed and Green Sleeves resists bolting, both useful for a leaf crop. Leaves can be cut at any time. Dill is an annual with a short growing season: the vegetative phase lasts about 90 days after sowing, and some 210 days pass from sowing to ripe seed. Its young twigs with needle-like leaves are used as a spice in dishes, fresh salads and processed vegetables, and in Polish cuisine fresh dill is the most widely used herbal spice. In a Serbian field trial the seed was harvested 45 to 70 days after flowering, in early September, before it began to fall, and yielded 1.6 to 2.1 tonnes per hectare. Dill grown at low density gives less leaf mass and more seed-bearing umbels than a dense stand, and it can be grown as a sole crop or alongside onions and carrots.

Open points

Whether flat-leaf parsley really tastes stronger than curly is disputed. The native range of dill is described in two ways that do not match exactly. The effect of dill heads or seed on the microflora of a cucumber ferment is not established. The apiol and myristicin figures for parsley come from one Mediterranean field trial and vary with strain and climate.