Seed Viability and Dormancy: Why a Seed May Not Germinate

A missing seedling has more than one possible explanation

You sow a labelled seed lot, keep a starting record and wait. Some seedlings appear; others do not. It is tempting to describe every missing seed as dead. But the visible surface tells you only that a seedling has not emerged there by the observation date. A seed may be nonviable, still dormant, in unsuitable conditions, slow to germinate or unable to emerge successfully.

The first step is to keep the questions separate. Is the seed capable of developing a normal seedling under suitable conditions? Have its germination requirements been met? Has germination actually begun? Has the seedling reached the surface and established? These are related questions, but they are not interchangeable measurements.

Use the earlier article on seedling goals and records to retain the seed identity, sowing date, original count and conditions. Shared Biology and Foundations explain cell growth and plant development; here the application is deciding what a seed observation can support.

Viability is a capacity; germination is an event

For planting, viability concerns the seed's capacity to produce a normal seedling under suitable conditions. It is not simply whether the seed looks intact. An embryo can be damaged inside an apparently sound coat, and visible firmness or colour alone cannot establish successful development.

Germination involves the resumption of embryo growth, commonly observed through the emergence of the embryonic root, or radicle, from the seed. A formal crop-seed germination result usually asks a further practical question: what proportion produces normal seedlings under the defined test? Always identify the scoring rule. A radicle count and a normal-seedling count can differ.

Emergence describes a seedling appearing above the growing medium. Establishment and later transplant readiness add further stages. A seed can begin germinating but fail to reach one of these later endpoints because of injury, disease, growing conditions or inadequate reserves. The stage you count determines what the result means.

First check the requirements of the species

Many cultivated seeds need an appropriate combination of water, oxygen and temperature for germination; light and gas requirements vary among species. Water uptake permits metabolic activity, but saturated conditions can restrict oxygen around a seed. Some aquatic species respond differently to low-oxygen conditions, so follow the actual species' requirements. Temperature also affects biological processes, and a setting suitable for one species may be unsuitable for another.

A viable seed that is prevented from germinating by an unfavourable external condition is not necessarily dormant. If the medium is too dry or the temperature is unsuitable, the environment itself can explain the delay. Dormancy instead involves a restriction associated with the seed, so favourable external conditions alone may not be enough.

Check species-specific guidance and your actual record before choosing a treatment. The elapsed time matters too: a count taken before a suitable test period ends can confuse slow development with failure. Do not choose a universal temperature, depth or deadline for every crop or wild species.

Dormancy has different mechanisms

Physical dormancy can involve a seed coat that is impermeable to water. Physiological dormancy involves processes in the embryo or surrounding tissues that restrict germination. Other forms exist, and some seeds combine mechanisms. A hard-looking seed coat does not by itself prove which mechanism applies.

Scarification is the controlled alteration of a coat to overcome a relevant physical barrier. Stratification involves an appropriate period of moist temperature treatment, which may be cold or warm depending on the species and its requirements. Dry storage in a refrigerator is not automatically equivalent to moist cold stratification.

Treatments need to match the actual species and seed condition. They can be unnecessary or damaging when applied indiscriminately. This article identifies the mechanisms; a practical propagation method should use suitable species-specific instructions, with treated and untreated seed identities retained in the record.

A test result needs its method and denominator

A sample test can inform you about a seed lot, but the sample should represent that lot. Picking only the largest or best-looking seeds changes the question. Record how the sample was selected, the number tested, the medium, temperature, light or dormancy treatments, test period and scoring criterion.

Calculate the stated result from that stated denominator. If an illustrative test uses 50 seeds and produces 34 normal seedlings, the normal-seedling proportion is 34 ÷ 50 = 0.68, or 68%. Keep abnormal seedlings and ungerminated seeds separately recorded. Do not count them as normal seedlings, and do not silently remove them from the denominator.

Different test protocols may define different denominators. For example, a seed-bank investigation can report germination among filled seeds after examining empty seeds; a crop-seed report uses its own prescribed categories and calculations. Neither result can be interpreted correctly if the reader does not know what was counted. A small home observation is useful, but it is not automatically a certified seed-laboratory result.

Further assessment can narrow the explanation

Examination can reveal empty or damaged seeds, while a carefully interpreted tetrazolium test can estimate viability through staining associated with living tissues. Such testing requires appropriate preparation and interpretation. A viability estimate does not replace the information supplied by a suitable germination test.

Dormancy becomes a stronger explanation when evidence supports viability, the test conditions meet the species' requirements, and the response to an appropriate dormancy treatment is consistent with the mechanism. A single failed tray, an attractive cut seed or a treatment that changes several conditions does not establish all of this.

Controlled test results also retain limits. Storage after testing, soil or medium conditions, sowing and later care can affect field performance. Use seed tests to inform a growing decision alongside the lot's history and actual site conditions; keep the earlier distinction between a planned quantity and an observed useful output.

Worked examples

Check your understanding

1. No seedlings are visible above the medium today. Can you label every missing seed nonviable?

   Show answer and reasoning

   No. You have observed absence of emergence at this time.

   Viability, dormancy, unsuitable conditions, elapsed time and failure after germination are different possible explanations.

2. Does a count of seeds with visible radicles always equal a formal count of normal seedlings?

   Show answer and reasoning

   No. The scoring endpoints differ.

   Visible radicle emergence indicates an event in germination. Normal-seedling scoring evaluates development against its test criteria.

3. Is keeping a dry seed packet cold necessarily the same treatment as moist cold stratification?

   Show answer and reasoning

   No. Moisture and the species-specific treatment conditions matter.

   The word 'cold' does not establish equivalent conditions or a suitable dormancy treatment.

Key ideas

• A viable seed has the relevant developmental capacity; a dormant seed can remain viable without germinating under otherwise suitable conditions.
• Lack of emergence alone cannot diagnose death or dormancy.
• Match germination conditions and any treatment to the actual species.
• Retain the test endpoint, categories, denominator and sample-selection method.
• Controlled test evidence informs production but does not guarantee field establishment.