Germination Test

A counted number of seeds, drawn from a representative sample of the lot, is placed on a substrate appropriate to the species under conditions of temperature, moisture, and light specified by the applicable rules. The test runs for a prescribed period, sometimes with an interim count and a final count, after which every seedling — and every seed that failed to produce one — is examined and classified. The rules governing all of this, down to how a "normal" seedling is defined structurally for each species, are set by the seed testing authority whose rules are being followed, not by this entry.

Standardisation is what makes the result usable: because the substrate and conditions are fixed by the rules rather than left to the tester's judgement, results from different laboratories following the same rules are broadly comparable, which is what makes seed certification and contract specification possible in the first place.

The test is deliberately run under near-ideal conditions so that a seedlot gets the best realistic opportunity to demonstrate its germination capacity. That design choice is also the test's central limitation: a real seedbed is rarely that favourable, and cold soil, excess or deficient moisture, surface crusting, seedling diseases, and mechanical impedance all reduce the proportion of sown seeds that actually establish, none of which the standard test is designed to capture. A high laboratory result is therefore a ceiling on what the lot can do under favourable conditions, not a forecast of field performance.

The germination test also does not measure vigour. Two lots can post the same germination percentage while performing very differently when sown into a stressed seedbed or after a period of storage; vigour testing exists precisely because germination capacity alone cannot answer that separate question, and it is carried out with different, deliberately more stressful test protocols.

Classifying a seedling as normal, abnormal, or dead requires an evaluator to compare what grew against defined structural criteria — the presence and condition of the root system, the shoot, and other essential structures, depending on species. This is a trained human judgement, not an automated measurement, and it is the largest single source of disagreement between laboratories testing splits of the same seedlot. It is exactly why the applicable rules are written in prescriptive detail and why evaluators are trained against reference material and periodically checked for proficiency: the rules exist to bound a source of variation that would otherwise be substantial.

Germination capacity also declines during storage, at a rate driven chiefly by the seed's moisture content and the temperature it is held at rather than by a fixed calendar interval. A certificate therefore describes the lot as it stood on its test date; a lot intended for a critical use such as sowing is normally re-tested closer to that use rather than relied on indefinitely.