What is Seed Dormancy

If a viable (living) seed doesn’t germinate at appropriate temperatures, with water and oxygen (and perhaps light too), it probably possesses dormancy.

The subject of seed dormancy has been active in a research sense for at least 100 years1, and has been known to exist for far longer. However describing exactly what seed dormancy is can be troublesome and numerous definitions have been accepted and rejected by seed scientists over the years.

A dormant seed is not a ‘failure’

Planocarpa test (1)

Figure 1. Planocarpa nitida (Ericaceae) at the TSCC; so far only a small amount of sporadic germination has taken place. Stone fruited Ericaceae seeds are frequently difficult to germinate.

Because dormant seeds don’t germinate, dormancy was, for many years, considered to be some sort of seed defect or inactivity that meant that even a viable seed simply could not germinate.

However investigation has proven that viable seeds, including dormant seeds, continually sense and respond to their environment2, so dormant seeds are not inactive.

Not only that but dormant seeds can germinate after dormancy has been removed or alleviated, and seedlings then develop normally. For more information, see topics covered under ‘Dealing with dormancy’.

Germination and dormancy are two very different things

Dormancy and germination work on different time scales and are affected by different environmental factors, (or are affected differently by the same environmental factors). We know this because seed scientists can make predictions about dormancy and germination separately3. For example, moisture, nitrate and light were found to influence germination of Polygonum persicaria (Polygonaceae) seeds, where as temperature influenced not germination, but dormancy status of the seeds4.

With regard to dormancy alleviation of Australian species, seed scientists are beginning to make a distinction between factors that affect dormancy and those that affect germination5.

Dormancy is not a matter of time

A seed isn’t dormant simply because it hasn’t germinated within a few weeks of germination testing. The time it takes for a seed to germinate can not be used to diagnose dormancy, unless germination tests last up to 90 days; the equivalent of a full season in the field (e.g. spring, autumn or ‘the rainy season’, etc.). If a seed is still viable after more than 90 days in germination conditions, and hasn’t germinated, it may be dormant (fig. 2).

Dormancy is not caused by environmental conditions

Gahnia trifida at 616 days.

Figure 2. Gahnia trifida (Cyperaceae) has shown slow and sporadic germination at the TSCC. These seedlings emerged following 616 days in germination test conditions!

The environmental conditions surrounding a seed do not cause seed dormancy. If a seed has no water, oxygen or temperatures adequate for metabolism and growth, it will not germinate, regardless of whether or not it possesses dormancy.

For example, seeds in a packet on the shelf in your garden shed will not germinate, but this doesn’t necessarily mean they’re dormant!

Instead this is called quiescence and is sometimes referred to as ‘pseudodormancy’6, or ‘enforced dormancy’7, but it is not really ‘dormancy’ at all.

Dormancy is a physiological block within the seed

Vleeshouwers et al. (1995)2 accurately described dormancy as …a block or blocks within the seed that prevent germination, as distinguished from the absence of factors required to evoke germination.

Dormancy is a seed characteristic

Vleeshouwers et al. went on to carefully described dormancy as ‘…a seed characteristic, the degree of which defines what conditions should be met to make the seed germinate.’

Other useful definitions of seed dormancy

A useful definition of seed dormancy will separate dormancy mechanisms from germination requirements, the process of germination and the environmental conditions surrounding the seed.

Simpson (1990)8 defined dormancy as: …temporary failure of a viable seed to germinate…in a particular set of environmental conditions that later evoke germination when the restrictive state has been terminated by either natural or artificial means.

Bell (1999)9 stated that seeds ‘must not be in a state of dormancy and the environmental requirements for germination of that seed must be met’, before germination can occur.’

Eira and Caldas (2000)10 defined dormancy as …a state in which the development or germination of a viable seed is blocked by one of many possible limitations located within the seed itself, and went on to discuss dormancy and germination as concurrent processes rather than in sequence.

Dormancy can range between all and nothing

Dormancy is today considered to be a ‘plastic’ seed characteristic, the status of which can range from any value between all (maximum dormancy) and nothing (non-dormancy). A non-dormant seed has the capacity to germinate over the widest range of normal physical environmental conditions possible for the genotype11.

For more on seed dormancy please view the following pages.


  1. Crocker W. 1906. Role of seed coats in delayed germination. Botanical Gazette. 42: 265-291.
  2. Vleeshouwers LM, Bouwmeester HJ and Karssen CM. 1995. Redefining seed dormancy: An attempt to integrate physiology and ecology. The Journal of Ecology 83: 1031-1037.
  3. Benech-Arnold RL, Sanchez RA, Forcella F, Kruk BC and Ghersa CM. 2000. Environmental control of dormancy in weed seed banks in soil. Field Crops Research 67: 105-122.
  4. Bouwmeester HJ and Karssen CM.1992. The dual role of temperature in the regulation of the seasonal changes in dormancy and germination of seeds of Polygonum persicaria L. Oecologia 90: 88-94.
  5. Merritt DJ, Turner SR, Clarke S and Dixon KW. 2007. Seed dormancy and germination stimulation syndromes for Australian temperate species. Australian Journal of Botany 55: 336-344.
  6. Hilhorst HWM. 1992. New aspects of seed dormancy. In: Proceedings of the Fourth International Workshop on Seeds. Basic and applied aspects of seed biology. 20-24 July 1992. Angers, France. Come D and Corbineau F, eds. 2: 571-579.
  7. Harper JL.1957. The ecological significance of dormancy and its importance in weed control. The 4th international congress of crop protection, Hamburg. 415-420.
  8. Simpson GM. 1990. Terminology and definitions of dormancy. In: Seed Dormancy in Grasses. Cambridge, England, Cambridge University Press: 43-59.
  9. Bell DT. 1999. The process of germination in Australian species. Australian Journal of Botany 47: 475-517.
  10. Eira MTS and Caldas LS. 2000. Seed dormancy and germination as concurrent processes. Brazilian Journal of Plant Physiology 12: 85-104.
  11. Baskin JM and Baskin CC. 2004. A classification system for seed dormancy. Seed Science Research 14: 1-16.

Why Does Seed Dormancy Exist?

From robust seed to vulnerable seedling; germination is risky business

Garden seedling

Figure 1. The time and the place for germination; getting it right is crucial to successful seedling establishment.

The process of germination represents a very risky step in the lifecycle of a plant.

The majority of seed-bearing plants disperse seeds that are desiccation tolerant which means they can withstand drying and remain viable in the soil for months or even years.

In contrast, most seedlings are highly vulnerable. At the seedling stage most of the plant’s features are poorly established; the roots are small, scant and have limited access to water, the leaves are small limiting their ability to capture light, protective structures / compounds are often missing or minimal and the process of seedling growth limits the plant’s resources.

Considering this move from robust seed to vulnerable seedling, it is not surprising that many plants try to ensure that seed germination takes place at just the right moment, in just the right place. Hilhorst1 summarised this idea in his definition of dormancy as, …a device for optimizing the distribution of germination over time and place.

Dormancy allows seeds to postpone germination

Rorippa germination

Figure 2. Rorippa gigantea (Brassicaceae) beginning to germinate on agar containing nitrate at 27/15°C.

Originally it was assumed that dormancy enabled seeds to survive long periods of environmental conditions unfavourable for germination2. However, ‘unfavourable conditions’ would lack germination stimulation features, preventing germination regardless of whether or not the seeds were dormant.

Better supported is the suggestion that dormancy enables seeds to survive short periods of favourable conditions; when germination stimulating factors are present, but prevailing conditions are not suitable for subsequent seedling growth and plant development34. In other words, the seeds have evolved to postpone germination until a time and place that not only supports germination, but also maximises seedling establishment and growth.

For example, seeds in Queensland postpone germination until after summer

In south-west Queensland, Asteraceae and Goodeniaceae seeds dispersed in spring were found to possess dormancy mechanisms that prevented immediate germination despite favourable pre-summer temperatures. Instead cooler autumn temperatures initiated germination only after dormancy had been alleviated over summer. Postponing germination until after summer presumably allows seedling establishment, growth and reproduction to take place during the cooler winter months instead5.

Soil seed banks; seeds ready and waiting

While seeds lie dormant in the soil, dormancy not only prevents premature seedling emergence, but also promotes the formation of a ‘soil seed bank’, a reserve of seeds in the soil which provides in situ conservation of the plant’s genetic variability6.

Dormancy and Germination Cycle

Figure 3. A diagrammatic representation of the timing of seed dormancy loss/induction and germination events for seeds released into the soil seedbank in Mediterranean climate areas of Australia. Adapted from Merritt et al. 2007.

Figure 3 gives a representation of how dormancy status of soil seed banks is understood to increase and decrease throughout the year in warm, temperate regions within Australia7. Changes in dormancy status are caused primarily by changes in temperature and seed moisture content. If non-dormant seeds do not experience appropriate germination conditions, dormancy will be re-induced; a phenomenon known as ‘dormancy cycling’ that may continue over several years until seeds germinate or lose viability.

Figure 3 also depicts at what time of year seeds experience the effects of dry after-ripening and stratification in situ in Australia’s warm, temperate regions. Please click on the links to understand more about how these treatments affect seed dormancy.

Dormancy is a challenge for those wanting to conserve seeds

It can be argued that there is little point conserving seeds unless we know how to germinate them. Dormancy is a complex seed trait present throughout the higher plants of all the world’s major climatic regions. The challenge for seed banks is to uncover the environmental cues that tell a seed it’s the right time and place to germinate.


  1. &  2. Hilhorst HWM. 1992. New aspects of seed dormancy. In: Proceedings of the Fourth International Workshop on Seeds. Basic and applied aspects of seed biology. 20-24 July 1992. Angers, France. Come D and Corbineau F, eds. 2: 571-579.
  2. Bell DT. 1999. The process of germination in Australian species. Australian Journal of Botany 47: 475-517.
  3. Vleeshouwers LM, Bouwmeester HJ and Karssen CM. 1995. Redefining seed dormancy: An attempt to integrate physiology and ecology. The Journal of Ecology 83: 1031-1037.
  4. Hoyle GL, Steadman KJ, Daws MI and Adkins SW. 2008. Physiological dormancy in forbs native to south-west Queensland: Diagnosis and classification. South African Journal of Botany. 74(2): 208-213.
  5. Nikolaeva MG. 2001. An update of Nikolaeva’s seed dormancy classification and its relevance to the ecology, physiology, biogeography and phylogenetic relationships of seed dormancy and germination. Botanicheskii Zhurnal 86: 1-14.
  6. Merritt DJ, Turner SR, Clarke S and Dixon KW. 2007. Seed dormancy and germination stimulation syndromes for Australian temperate species. Australian Journal of Botany 55: 336-344.