Where Sejak sits

Sejak is plucked from Gogu (공우, around 20 April) up to Ipha (입하, around 5 May) — bracketed by two solar terms rather than fixed dates. Both terms are astronomical, so the window shifts by about a day from year to year.

The hanja varies in circulation: 細雀 with the “sparrow” character, and 細茶 with the “tea” character. The bird reading comes from 작설 雀舌, “sparrow’s tongue,” an old description of the leaf shape. Both forms are in use in Korea.

Where Korean sources disagree

This is worth knowing because it explains inconsistencies you will meet across suppliers.

Hadong County defines all four grades by solar term plus leaf maturity — Jungjak, for example, as tea picked about ten days after Ipha once the leaf has grown beyond Sejak.

Osulloc, Korea’s largest producer, describes it differently: Ujeon, Gogu-cha and Ipha-cha are the date axis, while Sejak, Jungjak and Daejak are a size classification, all plucked around Gogu.

Those two accounts cannot both be complete. Korean authorities have not converged, and almost every English-language description collapses the whole thing into fixed calendar dates and loses the distinction entirely. If you are writing a menu or a spec sheet, the safest formulation is the one both sides agree on: Sejak is an early spring pluck, taken after the first flush and before the leaf coarsens.

Sejak is not the Korean sencha

This comparison comes up constantly and it confuses two different kinds of category.

• Sencha is a processing style — Japanese green tea that is steamed to fix the leaf.
• Sejak is a plucking period — it says when the leaf was picked, not how it was made.

Most Korean green tea, and Hadong’s in particular, is pan-fired (덮음) in a cauldron rather than steamed. That is the real divergence in the cup: pan-firing pushes the tea toward roasted, nutty and rounded notes, where steaming holds the marine, vegetal register that defines sencha. Two teas can share a plucking window and taste nothing alike.

Why Sejak is usually the right grade for a business

Korea is a small origin — 2,624 hectares producing 4,185 tonnes of fresh leaf in 2023, roughly 800 tonnes finished. Ujeon is a slice of that taken in a window a few days wide, which is why it does not exist in the volumes a hotel group or a distributor needs, at any price.

Sejak has a wider picking window, enough leaf development to hold a consistent profile across a season, and it still carries spring character. For a menu that has to taste the same in September as it did in May, that consistency is worth more than a scarcer grade.

On price, one Boseong producer’s organic line showed roughly an eightfold spread per gram between Daejak and Ujeon in the same season, with Sejak sitting in the upper middle of that range.

Cultivars, and a measured difference

Korea has bred its own tea cultivars — twenty-two registered with the Korea Seed & Variety Service by 2023. Two of them, Bohyang (보향) and Chamnok (참녹), were developed in Jeollanam-do and measured by the Rural Development Administration with Chonnam National University against the Japanese cultivar Yabukita: catechin content higher by 22.9% and 23.4% respectively, and cellular antioxidant effect higher by 16.2% and 18.2%.

Worth knowing because Yabukita is also planted in Korea, particularly on Jeju. When a supplier can name the cultivar, you learn something; when they cannot, that is information too.

Two questions worth asking

• Pan-fired or steamed? It changes the cup more than the grade name does.
• Which cultivar, and where? Jaerae-jong seed-grown tea from Hadong, a named Korean cultivar, and Japanese cultivar acreage on Jeju all sit under “Korean tea.”

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