What grinding actually does
The aroma of a seed sits in cells and oil glands that are intact until they are broken. Grinding breaks all of them at once and exposes an enormous surface area to air. Oxidation and evaporation then run for as long as the jar sits on the shelf, which in most kitchens is years. Nothing about the powder looks different after six months, which is precisely the problem.
The worst offenders
Nutmeg, allspice, grains of paradise, mahleb and cardamom lose their character fastest — mahleb is noticeably stale within weeks and is sold ground almost everywhere. Whole nutmeg keeps for years and takes ten seconds to grate. Cumin, caraway and nigella are more forgiving whole and still much better than the powder.
Where whole is not the answer
Some materials need breaking to give anything at all. Juniper berries have a tough skin and whole ones release almost nothing — crushing roughly doubles the extraction. Cardamom pods need cracking. Makrut lime leaf has to be torn because the oil is on the surface. Whole is a storage strategy, not a brewing one.
Toasting is a separate decision
Cumin, coriander, nigella and soybean are transformed by thirty seconds in a dry pan — raw and sharp becomes nutty and rounded. Fenugreek is the exception that proves the rule: it goes from nutty to acridly bitter in about ten seconds, and there is no recovering it. Toast before grinding, never after.
How to tell what you have
Smell it. A material that does not smell of itself in the packet will not taste of itself in the cup, and no brewing technique fixes it. This applies as much to shade-dried leaf and to lavender as to ground seed.