Two ways of grading, and what each assumes
A leaf-appearance system sorts finished tea by size, wholeness and tip content, and assumes that a buyer will taste before committing, so the grade only has to describe what is physically in the chest. A picking-date system classifies tea by when in the season it was harvested, and assumes that the season is the dominant determinant of character, so the date stands in for the whole description. Both assumptions are defensible in the industries that hold them. The letter grades belong to the orthodox black tea trade of South Asia and East Africa, where lots are bought at auction by professionals; the date ladders belong to the green tea traditions of China, Japan and Korea, where the annual cycle is short, the premium sits at the start of it, and consumers have been buying by season for a long time. Neither system translates. A buyer who has learned the letter ladder and then looks for its equivalent on a Korean or a Japanese pack will not find one, and will miss the field that is actually doing the work.
The Korean ladder
Korean green tea uses the clearest and most explicitly calendrical of the picking-date systems. Ujeon denotes tea picked before the seasonal division conventionally associated with the arrival of the spring rains; sejak names the next picking, of small young leaf; jungjak follows; and daejak denotes the later, larger-leaf harvest. The ladder is a ladder of time and of leaf maturity together, since the two move as one, and it maps onto price directly. What it does not do is describe processing, which in Korean tea varies considerably between producers and regions and is a separate question. Nor does it settle preference: the earlier pickings are more delicate, sweeter and more expensive, and the later ones have more body and briskness, and a drinker who prefers a fuller cup will find the top of the ladder disappointing at several times the price. The pattern is worth naming because it recurs in every picking-date system in this page: earlier means scarcer and more delicate, later means fuller and cheaper, and neither is a synonym for better.
The Chinese calendrical terms
Chinese green tea is distinguished by whether it was picked before Qingming in early April, before Guyu later that month, or after, and the vocabulary is calendrical rather than a numbered ladder. The mingqian premium is large and is real for a well-understood reason: the earliest shoots grow slowly out of the plant’s winter reserves in cool weather and modest light, and that leaf is generally richer in the amino acid fraction relative to the polyphenols. It is also the single easiest premium in tea to game, since an early-budding cultivar reaches market before a famous tea does and can be shaped and sold as it — the Wu Niu Zao and Longjing case the catalogue records as a routine substitution. Two qualifications keep the terms honest. The festival dates are fixed and the weather is not, so an early spring and a late one produce quite different teas under the same designation. And the terms apply meaningfully to a picking window in a particular place, so a mingqian claim for a region whose season runs on a different schedule is a claim that has been borrowed rather than made.
The Japanese pickings, and where they differ
Japanese classification numbers the harvests — ichibancha, nibancha and onwards — and uses shincha for the new tea of the season as a commercial category on top of that. The distinctive feature of the Japanese system is that the picking is paired with a product type rather than standing alone: later pickings are not simply lower grades of sencha, they are the raw material for bancha, hojicha and genmaicha, which are separate products designed around what that leaf is good at. That is a more useful arrangement than a pure ladder, because it removes the implication that later tea is failed early tea. It also means that reading a Japanese pack requires both fields together, since an ichibancha bancha and a nibancha sencha are both real and both slightly unexpected. The pairing is one reason Japanese labelling is the most informative in common circulation, and it is a good argument for the general principle that a classification works better when it says what a thing is for than when it says where it sits.
Why the date can be more predictive than the appearance
For categories whose value sits in the amino acid fraction and the fresh aromatic top, the season sets the composition and the appearance mostly follows from it, so the date is upstream of the thing a grade would be describing. For fully oxidised black tea the relationship is weaker, because processing decisions dominate and the leaf-appearance grade describes what will happen in the pot. That is the structural reason the two systems grew where they did rather than one being more advanced than the other. It also explains a practical asymmetry a buyer can use: for a green tea, a stated picking window with no grade is more informative than a stated grade with no date, and for an orthodox black tea the reverse holds. Where a seller provides both, the pair narrows the tea considerably. Where a seller provides neither on a premium-priced tea, that is the observation to make, since both fields are cheap to print for anybody whose supply chain recorded them and expensive to print for anybody whose did not.
The failure modes of a date ladder
Three, and they mirror the failure modes of the letter grades rather than avoiding them. Self-assignment: nobody external verifies a picking claim, and a date is as printable as a superlative. Cultivar gaming: an early-budding variety produces a genuinely early tea that is early for the wrong reason, and the ladder cannot distinguish them. And regional drift: a designation developed for one production area applied to another, where the calendar does not correspond, describes nothing. Against those, date ladders have one advantage the letter grades lack — they are falsifiable in principle. A tea claiming an early spring picking should look and smell like one, with bright dry leaf, a vivid aroma and the aromatic top present in the first infusion, and a green tea claiming this year’s picking that reads flat and olive is answering the question regardless of what is printed. That is a check a drinker can run without expertise, and it is why the catalogue rates a picking claim as the more useful of the two kinds of grade for the categories it applies to.