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Ten thousand three hundred and thirty five tonnes of roses in 2024. About six thousand tonnes in 2025. The same valley in Bulgaria, the same rose, the same pickers. The only difference was a warm winter and a cold spring. This piece uses the library's harvest calendar as a map of time, to read why every bottle of essential oil carries a season and a year.

May in the rose valley

The Damask rose does not wait. The picking season in Bulgaria lasts about 20 to 25 days, usually starting in May and sometimes running into early June. The growing area lies in the centre of the country, in the valley between the Stara Planina range to the north and the Sredna Gora to the south, around the town of Kazanlak, a place often called the Valley of Roses. Bulgaria and Turkey are the two largest sources of Damask rose oil in the world.

The flowers are picked by hand from about 5 or 6 o'clock until about 11 or noon, when they have just opened and still hold most of their volatile compounds. The geographical indication for Bulgarian rose oil requires the flowers to reach the still no later than 10 to 15 hours after picking. Each cubic metre of still takes about 100 kilograms of flowers, mixed with water at a ratio of 1:4 to 1:5. About 3,500 kilograms of flowers are needed for one kilogram of oil.

The still leaves its own mark. Phenylethyl alcohol, the molecule that carries the smell of fresh roses, dissolves well in water, so most of it stays in the distillation water. The geographical indication caps it in Bulgarian rose oil at 3 percent. The name Bulgarsko rozovo maslo has been protected nationally since 1994 and was registered by the European Union in 2014; rose distilling in the region has been recorded since the seventeenth century.

On the May calendar page, the library lists 29 harvests under way across 13 regions. Bulgarian Damask rose, Bulgarian white rose, the May rose of Grasse, violet leaf, Turkish Damask rose and Kushui rose from China all begin their season. For perfumery, May is the month of the rose in many regions at once.

Summer in the lavender fields

Lavender is cut when the flower spikes open, then steam distilled. In Bulgaria the cutting happens in early summer, and the library calendar shows the Bulgarian true lavender season closing in July. True lavender oil, Lavandula angustifolia, is mainly linalool and linalyl acetate, the two molecules behind most of the floral, slightly sweet, slightly herbal smell of the plant.

The lavender map has changed within a little over a decade. In 2012, when French output fell because of a bacterial disease, Bulgaria became the largest producer of lavender oil. Its area grew to about 18,000 hectares, five times larger in roughly ten years, and the two countries together account for nearly three quarters of world production. According to the Bulgarian essential oil industry association, Bulgarian oil has a more distinctly green, grassy top note than French oil.

July on the library calendar has 28 harvests across 13 regions. Grasse jasmine and tuberose begin their season, and so does may chang in China. In the southern hemisphere, Madagascar opens its green vanilla harvest around the end of June and July. One month on the calendar holds many different seasons at once.

Cassia peeling and star anise picking

Not every raw material is a flower. In Văn Yên, cassia is peeled in two rounds, the second to third and the eighth to ninth lunar months. Vietnamese cassia oil is rich in cinnamaldehyde, about 90 percent. Cassia growers measure the season by the lunar calendar, not the solar one, and the library's harvest calendar records it that way.

Star anise in Lạng Sơn has its main harvest in August and September, and a smaller one in March and April. The eight pointed fruit is picked and distilled, giving an oil with trans-anethole at about 87 to 90 percent. These two materials have their own stories in Cassia · Bark from Trà My to Văn Yên and Star Anise · Eight Points from Lạng Sơn.

Cajuput in Huế shows another kind of season. The leaves are cut in the dry season, when the 1,8-cineole content runs higher; cajuput oil usually holds about 40 to 60 percent of this molecule. Here the season does not decide whether there is material or not, but what that material contains.

Flowers picked before dawn

The hour of picking is part of the season. Jasmine is picked at dawn; in Grasse, the picking of Jasminum grandiflorum must end before noon, and the flowers must reach the factory within three to four hours. In Egypt, jasmine grandiflorum flowers from June to November, with a peak from July to September. In India, jasmine sambac flowers for many months of the year.

Bulgarian roses have their own window: from about 5 o'clock until nearly noon. Ylang ylang in the Comoros and Madagascar flowers year round in flushes, and is picked early and distilled the same day. Three flowers, three ways of counting hours, one principle: the shorter the time between flower on the branch and flower in the still, the fewer volatile molecules are lost.

Some materials have almost no season. Patchouli in Indonesia is cut year round, the first cut after about six months. Vetiver in Haiti is dug year round. Atlas cedar in Morocco is distilled from sawdust and wood waste, following the rhythm of the sawmills. For these materials the calendar records not a picking season but a cutting rhythm. Even then, each cut is still its own batch, with its own distillation date and its own lot number on the drum; the calendar records only what can be recorded, and the rest lives in each distillery's ledger.

A good year, a bad year

Spring weather decides almost the whole Bulgarian rose harvest. Only about one percent of the rose area is irrigated. In 2024 the country picked 10,335 tonnes of flowers. In 2025 the crop fell by about half, to around 6,000 tonnes: a warm winter, then a cold spring, and frost in more than half the gardens. In 2018 to 2020 the rose harvest had reached about 20,000 tonnes a year.

Lavender has its own curve. Fast growth in Bulgarian planting led to oversupply; the oil price fell from about 120 euros per kilogram in 2018 to about 60 euros in 2020. Then the drought of 2021 cut yields by about half. One year of surplus, one year of shortage, the same field.

Weather changes not only the tonnage but also the composition. The geographical indication for Bulgarian rose oil sets ranges: citronellol 24 to 35 percent, geraniol 13 to 22 percent, nerol 5 to 12 percent. Those ranges are wide enough to hold the differences between years, and narrow enough to detect adulteration. Two samples of Damask rose oil that both meet the standard can still smell different.

The Bulgaria page in the library notes one more detail of distilled rose oil: nonadecane and other long chain hydrocarbons crystallise into white flakes when the oil is cold. That is normal, not a sign of spoilage.

The season inside a lot number

A drum of essential oil carries its year and its region. When a supplier sends a new batch, each drum is labelled with the botanical name, growing region, production lot and extraction date. Those lines are a shortened version of the harvest calendar: where the plant grew, and when it was distilled.

At Lê Mai, once a sample passes GC-MS and sensory checks, each batch receives a lot number entered in a dedicated ledger, made of the intake date, the supplier code and the sequence number of the batch in the year. Every product made from that batch carries the lot reference. Two lots of lavender from the same species and supplier but different years are two different batches in the ledger, and can be two slightly different smells on a blotter. The process is recorded in A Batch of Essential Oil Has Just Arrived.

Reading a lot number is therefore also reading a season. Each lot of essential oil is a slice of one year, in one region, through one still. A bottle of Bulgarian rose oil from 2025 comes from a short flower harvest. A bottle of Bulgarian lavender from 2021 comes from a drought year. No label records the weather, but the weather was in the oil before there was a label.

Twelve months, fifteen regions, each with its own rhythm.

A bottle carries no picking date on its label.

It still remembers the month it was distilled.