What gets picked
Oolong is picked as open, mature leaf rather than as bud, which surprises people who assume all fine tea is young leaf.
A rock tea pluck is typically the 3rd or 4th leaf, with the bud long since gone, described as an open face.
Ball rolled styles such as Tieguanyin take a slightly tighter standard, usually 2 or 3 leaves.
High mountain oolong sits between the two, at 1 bud with 2 or 3 leaves.
What all of them share is maturity, because the leaf has to survive being shaken hard and repeatedly.
Bud and fine tip are not the goal here, and a pluck of pure tips would bruise into a mess within an hour.
The standard is described by how open the leaf is, from a small open face to a large one.
Pickers read that by eye and by hand, which is why experienced pickers earn more per kilo.
Leaf that is too young goes red at the edge and then black, because it cannot take the abrasion.
A pluck that is too old gives a hollow, woody tea with nothing left in the middle of the cup.
Why the standard exists
The reason is mechanical before it is chemical, because oolong is made by bruising the leaf edge.
Shaking, or yao qing（摇青）, rubs leaf against leaf for hour after hour across a day and a night.
Tender leaf tears under that treatment, and torn leaf oxidises unevenly and turns sour.
Mature leaf has a cuticle and a fibre structure that survives the shaking and keeps the leaf centre green.
That contrast, red at the rim and green at the middle, is the whole point of oolong making.
Chemistry follows the mechanics: mature leaf carries more of the precursors that become aroma while it withers.
Young leaf is rich in amino acids, which suits green tea but gives oolong a thin and flat result.
So the plucking standard is not a mark of refinement here, it is a requirement of the process.
Pick bud for oolong and you remove the very thing the maker needs in order to work.
The factory cannot add maturity later, and no amount of skill fixes a pluck that came in too young.
Grade follows the leaf
Grade in oolong is read from the made leaf and the cup, but both are decided at the pluck.
Evenness is the first thing a buyer sees, because a mixed pluck oxidises at two different rates.
One open face across the batch gives one fermentation, and that uniformity is what grades reward.
The site matters as much as the standard, since the same pluck from two valleys is not the same tea.
Within a site, later plucks are coarser, and the price follows the leaf down through the season.
Hand picking gives a cleaner standard than shearing, which is why machine plucked oolong grades low.
Machine cutting takes whatever is at the height it is set to, mixing bud, open leaf and old leaf.
That mixture cannot be made evenly, so it is sold cheaply or blended away into a lower grade.
Hand plucked leaf also arrives whole, and whole leaf survives the tumbling with its structure intact.
Grade is therefore a record of decisions made in the field, not a judgement applied afterwards.
Season and timing
Oolong has 2 main seasons, spring and autumn, and they produce recognisably different teas.
Spring leaf grows slowly in cool weather, and the tea made from it is thicker and more substantial.
Autumn leaf grows fast in dry weather, and the aroma is higher while the body is lighter.
Many producers value autumn for fragrance and spring for weight, and price them accordingly.
Within the day, pickers wait for the dew to dry, which usually means late morning onward.
Leaf picked wet heats in the basket and starts to ferment before anyone intended it to.
Afternoon leaf, called noon leaf, is prized because it reaches the factory already partly withered.
Rain stops picking altogether, since wet leaf cannot be controlled through the withering stage.
A spring pluck runs for a few weeks at most, and the best material comes from perhaps 10 days of it.
Everything the maker does afterwards is an attempt not to waste what those weeks produced.