A dried fruit the colour of wood, eight points arranged in a star, each point holding one glossy seed. Lạng Sơn grows 43,370 hectares of the trees that bear it, and almost all of its scent lies in one molecule: anethole.
The eight pointed fruit of Illicium verum
The star anise fruit is not a flower, although in several languages it is named as one. It is a compound fruit made of eight small follicles arranged around an axis, each follicle splitting into one point and holding one seed. Once dried, the points harden, the colour turns to wood brown, and the star shape becomes clear.
The tree is Illicium verum, a small evergreen of the family Illiciaceae. The library records it as native to southeast China and northeast Vietnam. Trade names include đại hồi, hoa hồi, star anise and badian. The star anise page in the Lê Mai library keeps all of them.
In Vietnam, Lạng Sơn star anise is the name most closely tied to the tree. Lạng Sơn has 43,370 hectares of star anise, about 70 percent of the national area, of which about 28,000 hectares are bearing fruit. Quảng Ninh has about 8,600 hectares, Cao Bằng about 4,500. The country harvests around 22,000 tonnes of dried fruit a year, second in the world after China.
Star anise needs the cool climate of the northern limestone mountains. That is why the map of Vietnamese star anise almost matches a handful of border provinces. In 2025 Vietnam exported 14,307 tonnes of star anise, worth 58.7 million USD. Most of it leaves as dried fruit, for the spice trade; a smaller share goes into the still.
Another tree gives an almost identical fruit. Japanese star anise, Illicium anisatum, is toxic, and once dried it is nearly impossible to tell apart from true star anise by eye. That detail returns at the end of this piece.
Two harvests in Lạng Sơn
The star anise tree fruits twice a year, and the two crops are not the same. The main crop, called hồi mùa, ripens around August to September; the fruit is large, with thick points. The secondary crop, called hồi tứ quý, comes around March to April and gives less fruit.
The harvest months recorded in the library for star anise are March, April, August and September, matching those two crops. Harvest months can shift by about a month between years and between areas, depending on weather. These figures are a frame, not fixed dates.
After picking, the fruit is sun dried or kiln dried. Dried fruit is the main commodity: it goes into spice blends, into broth, into the wholesale markets on the border. In Vietnamese cooking, star anise is one of the scents recognised at once in a bowl of phở. Essential oil is only a small branch of that flow.
Lạng Sơn star anise has been protected as a geographical indication since 2007, number 00007, one of the first geographical indications in Vietnam. The file names the fruit as the protected product. For an aromatic crop, being registered that early shows its place in the economy of the northern mountains.
Two crops, one tree, one mountain region. The scent of star anise changes little between the main and secondary crop, but the size of the fruit and the yield do.
Distilling the dried fruit
Star anise oil is steam distilled from the fruit, and can also be distilled from the leaves. The library notes that the fruit is dried first and then distilled. Steam passes through the mass of fruit, carries the volatile molecules with it, and condenses into a layer of oil that separates from the water.
Vietnamese samples gave about 90 percent trans anethole in fruit oil and about 87 percent in leaf oil. The library's wider data give star anise oil (E) anethole from 71.2 to 91.8 percent. It is one of the most concentrated essential oils in composition.
The rest of the bottle is made of smaller constituents. Foeniculin from 0.5 to 14.6 percent. Estragole from 0.3 to 6.6 percent. Limonene up to about 5 percent, with linalool, alpha pinene and beta caryophyllene at about one to two percent each. Safrole may be present at a very low level, up to 0.1 percent.
That concentration is what makes star anise oil easy to adulterate. The library notes the oil is often cut with technical anethole, a grade with a relatively high share of (Z) anethole. (Z) anethole is more toxic than the (E) form. In genuine star anise oil the (Z) form appears only from trace to 0.4 percent; that figure is a signal when reading an analysis sheet.
The still adds nothing to the fruit. It only separates the volatile part from the woody part. What sits in the bottle is what the fruit carried from the tree.
Anethole: one molecule, three plants
Three plants that are not close relatives give the same sweetness. Star anise belongs to Illiciaceae. Aniseed, Pimpinella anisum, and sweet fennel, Foeniculum vulgare, both belong to the carrot family (Apiaceae) and are herbaceous plants of the Mediterranean. What they share is not their shape but a molecule.
(E) anethole has the formula C₁₀H₁₂O and a molecular weight of 148.20 g/mol, and belongs to the phenylpropenoid ethers. The library describes its scent as liquorice, anise, sweet and warm, almost the definition of the anise note. Anethole is also sweet in taste: one reference records it as 13 times sweeter than sugar.
Anethole content in the three oils is close. Aniseed oil holds 75.2 to 96.1 percent. Sweet fennel oil holds 58.1 to 92.5 percent. Star anise oil holds 71.2 to 91.8 percent. All three carry a small amount of estragole, a molecule structurally close to anethole.
The difference between the three bottles lies in what remains. Star anise has foeniculin and a little safrole. Sweet fennel adds limonene, up to 21 percent, and fenchone, up to 8 percent. Aniseed is almost pure anethole. On a blotter, star anise is warmer and rounder, sweet fennel has a green edge, and aniseed is the most direct and the sweetest.
Anethole is also why some anise spirits turn cloudy when water is added. The molecule dissolves in alcohol but not in water; when water goes in, anethole separates into very small droplets, forming a milky white microemulsion. The phenomenon is called the ouzo effect. One molecule, three plants, and a glass that changes colour.
Why star anise oil solidifies in the cold
A bottle of star anise oil left through a cold night may show white crystals, or thicken into a cloudy mass. This is not a sign of spoilage. It is a physical property of the molecule that fills almost the whole bottle.
Pure anethole has a melting point of about 20 to 21 degrees C. At room temperature on a warm day it is a liquid. When the temperature falls below that, the molecules begin to line up into crystals. An oil that is up to nine tenths anethole carries that property with it, although the other constituents bring the actual solidifying point of the mixture a little lower.
In Lạng Sơn, winter brings very cold nights. A drum of star anise oil in a store room can set solid, then melt again when the weather warms. For a perfumer this means the bottle should be warmed gently until it runs clear before weighing, so that the solid part does not hold a different share of anethole from the liquid part.
One distinction matters: star anise oil left exposed to air oxidises, forming (Z) anethole, anisaldehyde and anisic ketone. The library notes these oxidation products may raise the risk of sensitisation. Oil that sets in the cold is normal; oil that changes its scent with age is not.
Star anise on skin: limits of use
The limit on star anise oil does not come from anethole but from two small companions. The library notes that (E) anethole itself is not carcinogenic in rodents. The concern lies with estragole and safrole, two molecules structurally close to anethole but with a different toxicity profile.
From this, the maximum dermal level for star anise oil is 1.75 percent, based on an oil sample with 6.6 percent estragole and 0.1 percent safrole. Under IFRA and EU rules, safrole is limited to 0.01 percent in cosmetics. For sweet fennel the maximum dermal level is 2.5 percent.
Anethole shows weak estrogen like activity in laboratory tests. The library therefore lists star anise oil as contraindicated by all routes in pregnancy, breastfeeding, endometriosis and estrogen dependent cancers, and for children under 5. This is safety data, not advice about use; this piece says nothing about effects of star anise on the body.
Japanese star anise needs repeating here. Illicium anisatum is toxic, and the library notes that cases of neurotoxicity in infants linked to star anise tea are usually due to contamination with this species. In 2003 the US Food and Drug Administration warned about star anise teas after about 40 poisonings. As the essential oils of Vietnam page puts it, clear provenance comes first when buying the fruit or the oil.
A limit of 1.75 percent still leaves star anise plenty of room in a formula. It only records that a sweet molecule can travel with others that are not so sweet.
Eight points, one seed in each, nine tenths a single molecule.
Twenty one degrees is the line between liquid and solid.
The rest of the scent of star anise lies in small numbers after the decimal point.