Germination Test

A germination test samples for total viability, including the sum of all seeds (of a “kind” listed on the label) actually germinating using standard laboratory methods + hard seed and/or dormant seed.

• Percent Germination: A germination test determines the capability of a seed lot to produce normal seedlings under favorable controlled conditions. Total germination is the percent germination added to the percent hard and/or dormant seed. Anything under 100 percent total germination represents the presence of dead seed and/or seed that doesn’t produce a shoot or root. Germination may also be estimated by the use of a tetrazloium chloride test (TZ test) in which seeds are stained with a dye to determine viability. Viable seed with live (respirating) tissues will stain a red color. However, not all states recognize the use of a TZ test for all species.
• Dormant Seed: Includes hard seed, refers to the portion of the seed sample that doesn’t germinate during the seed test. Reasons for dormant seed are: 1) the seed coat is impervious to water, and/or 2) internal structures within the seed prohibit oxygen exchange. Hard seed may germinate at a later date and produce a viable plant, or it may germinate and succumb to competition, or it may never germinate at all.

The higher the germination percentage, the better. Germination of most grass species is normally above 80 percent and should not be lower than 60 percent. Germination of some native grasses, forbs, and shrubs may be lower, but can vary widely according to species.

Germination tends to decrease in all seed as it ages and some species loose germination more rapidly than other species, even under ideal seed storage conditions. For example, winterfat and forage kochia are noted for having a very short seed life and may be viable for only 1 to 2 years. Most species maintain germination at constant levels for several years and then slowly begin to decline as time passes. The rate of decline in germination varies widely between species as well as between seed lots of the same species.

The germination test date should be current due to the natural decline in germination over time. Grass, forb and legume seed should be updated every 9 to 18 months depending on state laws. Flower, shrub and tree seed should be updated every 9 months.

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Last Modified: 07/05/2007