On four axes at once: cut size, colour, leaf-to-stem ratio and volatile oil content. There is no single grade letter. Trade names such as “tea bag cut” or “standard cut” are conventions that mean different things in different houses, so a grade is only enforceable when the contract describes it in measurable terms.
Why it works this way
Cut size is the axis buyers notice first, and it is best written as a sieve fraction: passing one aperture, retained on another, with a maximum fines percentage. Fines are not a cosmetic issue – they carry a higher stem and dust share and they segregate during transport.
Colour is the visible proxy for gentle drying and short field-to-dryer time. It is normally assessed against a retained reference sample, though instrumental colour measurement in a defined colour space is available and is worth using when two origins are being compared.
Leaf-to-stem ratio is a yield question rather than a defect. Stem carries less volatile oil, weighs more per unit of flavour and looks coarse in the pack, so buyers who care write a maximum stem percentage.
Volatile oil is the axis most often left out and the one that determines whether the herb performs. It is reported on a dry basis and has to be read with the moisture figure.
What follows in practice
Specify all four, each with a number and a method, plus a retained reference sample refreshed each season. Then verify the delivered lot against the sample on a weighed sub-sample rather than by eye, because grade drift between the offer and the delivery is the most common commercial dispute in this category.
The dried oregano record shows how the four axes interact on one commodity.