Germination, Sowing and After Care Information for
Cork Oak (quercus suber)
Cork Oak acorns contain no natural dormancy and they will begin to grow whenever the conditions are right for germination, if they are not sown immediately the real problem is how to store them without rapid deterioration occurring.
It is perfectly possible for these seeds to begin to germinate during their passage through the postal system. In such a case they need to be planted immediately on arrival. Seeds of the oak species can sustain root breakage with no detrimental effect and the emerging root can be snipped off at about 1 cm from the emergence point on the acorn if excessive root growth needs to be controlled. The seedling will produce a more fibrous root system as a result.
For sowing deep containers are required to accommodate the strong taproots of this species. Pots at least 20cm should be used and serious growers should consider using modules such as root trainers that allow air pruning of the roots to take place. These allow the production of superb young plants with no root distortion. Planting in shallow containers will cause severe root deformation
Fill your chosen container with a good quality compost and press the seed into it to a depth of a couple of cm's (just under 1 inch) The orientation of the seed is not critical, generally speaking it is best if the root emerges to one side of the seed. Make sure that the seed is covered, watered and place in a frost free place for germination to begin. If the seeds of the species become frozen they will die! The seeds can be planted in Autumn left to produce a taproot and then left quiet through the winter in a cool but frost free place. In the Spring these seeds will quickly emerge and begin growth and will have a significant head start over Spring sown seeds.
If you do need to store your seeds you can mix them with dry peat and place them in a cool, dry, frost free, mouse free place through the winter. The bag that they are placed in should not be tied! If the peat is even slightly moist the seeds will begin to grow. The peat keeps the seeds separated which prevents them from sweating and heating. It also allows them to respire but not dry out too much. If you keep the seeds dry in a bag until Spring it is very likely that they will be dead before they are sown.
Initial shoot growth is very rapid and within a few weeks from germination the seedlings will be between 10 and 20 cm high. The trees will then rest for a few weeks before developing a terminal bud that will break into rapid new growth if the conditions are right. This usually brings height growth to 20 to 40c m. To encourage maximum growth ensure that the trees are never stressed because of a lack of water and that they are well nourished and grown in a warm, sunny position.
Trees should be planted in their permanent position as soon as is practical. If they are large enough, at the end of their first growing season and certainly at the end of the second. Allowing them to be grown in too shallow a container for any length of time will cause permanent root deformities that can lead to the failure of the tree once it grows to a large stature.
Acorns occasionally contain large white grubs, these are often not evident when the seeds are collected and emerge at a later date, sometimes during the delivery process. They, more often than not do not seriously harm the seed.