Hi, welcome to Taiga Bonzai in this post albeit short, we discuss the subject of germination because there is no guarantee that it will occur due to various factors.
Introduction – germination is the process by which an organism grows from a seed, spore or similar structure. The seed of a plant a relatively small package (although there are exceptions) is produced in a strobilus, (cone) carpel (fruit) or legume (pod) after the union of male and female reproductive cells. However, it should be noted that not all unions are successful, hence the seed/s lack embryo/s and will never germinate. In addition, some plants produce varying numbers of seeds that lack embryos; these are also infertile. Fully developed mature seeds in most plant species carry food reserves wrapped in a seed coat that splits open when the embryo begins to germinate.
Seeds – from certain fruit and vegetables for example, pomegranate, citrus (lemon-mandarin) and chilli varieties obtained from the supermarket have the ability to germinate, but many others will not because they are immature, have no embryo and thus are sterile. Another factor concerning germination failure is because the fruit when picked was unripe, hence the seeds have not reached the maturity required for germination. With some apple varieties it is possible to grow a tree from seed, but it will be genetically different and usually inferior to the parent tree and any fruit produced will not be the same. Most apple trees are propagated by grafting allowing growers to produce trees that are genetically identical to one another.
In nature trees have particular ways of dispersing their seeds by the wind, by animals and birds that consume and dispense them through their digestive system. Such seeds released from the parent plant are in what is termed as a dormancy stage, and dormancy is a natural state of being in many plants, its function is to ensure that the seed will germinate at an appropriate time. However, seeds can remain in a dormant state and fail to germinate although conditions, temperature, water and light are in adequate supply.
Dormancy – why this phenomena occurs can be attributed to a seed’s morphological and physiological requirements, because seed dormancy is able to originate in different parts of the seed, for example, within the embryo or its coating – the shell or husk. Thus, dormancy can be deemed not as a constant, but as a variable because it is a common phenomenon encountered in a large variety of trees. To break dormancy and initiate germination, the process of stratification is needed and this method requires different techniques of which, there are various approaches depending on a particular species of seed.
Seeds having two dormancy combinations, a seed coat dormancy and an internal dormancy (embryo) require the seed coat or shell to be treated first either by soaking in water and/or scarification. The internal dormancy is then subjected to the following treatment. Cold to break bud dormancy then warm temperatures to initiate root growth and to encourage the shoot to sprout and complete the germination process. There are various methods of scarification and stratification, but the most common approaches are: Cold stratification – Warm stratification – Warm and Cold stratification. The article on stratification and scarification can be found on this site ‘The stratification of seeds’ January 29th 2017
Some seeds including the pomegranate, Punica granatum the lemon and mandarin orange genus Citrus, a popular choice among bonsai enthusiasts can be stratified in a warm environment quite easily. Wash and dry the seeds to remove any fruit residue to prevent any attack from pathogens and fungal attack which, can cause the seed to rot. Then plant them in a propagator or sealed container with a moist soil medium and place in a warm environment temperature between 18-24°C. (65-75°F) You can use moist soft kitchen paper under and over the seeds as an alternative to to using soil.
Other common factors contributing to germination failure are: Old or unviable seeds – Unclean containers that may be contaminated with pathogens – wrong soil medium – wrong time of year – inadequate temperature – planted too deep – and insufficient water or over water. Why not have a go at growing plants from seed, it is a cheap and easy method in obtaining trees – an experimental learning curve; until next time BW, Nik.