Harvest timing
When a spice is picked decides its character: green, ripe or dried peppercorn, bud or open clove.
Also: picking stage, ripeness of spice, green vs ripe
A single plant can yield different spices depending on harvest. Black, white, green and red pepper are berries picked at different stages and processed differently. Clove buds are gathered just before they open; once flowering, the oil content falls. Cardamom pods are picked when full but still green. Chillies are green when unripe and red when ripe, and chilli powders vary accordingly. Vanilla beans are picked partly yellow. Coriander leaf and coriander seed come from the same plant at different times. Timing also interacts with weather, as rain at harvest can spoil drying. Experienced pickers judge by colour and feel.