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Trees can be raised from freshly collected or commercially obtained seed.
Different species may require different treatment to help them overcome dormancy.
For example, hard coated seed, may need the coating softened or chipped to allow germination to take place, others may require stratification.
To soften; place seed in a container, boil a kettle of water, allow boiled water to go just go off the boil and pour it over the seed.
Allow the water to cool, repeat this process twice more or until the seed sinks.
To chip; nick the seed coat with a knife, or scarify it by rubbing it with a file or sandpaper.
This will allow moisture to quickly penetrate the seed as opposed to the lengthy natural softening period in the soil.
Sow immediately after either treatment.
Some seeds develop germination inhibiting mechanisms when they ripen, so to avoid this, collect seed before it has fully ripened and sow it immediately.
n.b . Commercially obtained seed may have been collected after these inhibitors develop, and may take two years to germinate, a process sometimes referred to as 'double dormancy'.
That is; in their first year the seeds will naturally experience of summer warmth (warm stratification) and in the second winter they are chilled (cold stratifcation) before germinate the following spring.
To speed the process up, place seed in a clear plastic bag filled with a moist, open-textured mix of peat or composted bark mixed with coarse sand or perlite.
Seal the bag and keep it at 18°-24 ° C (65°-75 ° F) for up to 12 weeks, before subjecting it to a period of cold stratification.(see below)
n.b . Some species do not require this period of warm stratification, but may require ‘cold stratification’
This is carried out as follows;
Place seed in a clear plastic bag filled with a moist, open-textured mix of peat or composted bark mixed with coarse sand or perlite.
Place bag in a refrigerator, keeping it below 5 °C (40°F) for about 12 weeks depending on the species.
Shake the bag periodically, and sow seed immediately it has germinated.
Natural, fluctuating cold is more effective, so leaving seeds outdoors is generally more successful than keeping in a refrigerator.
Week 13-15; sow seed into 70mm (3”) pots of gritty potting compost.
Cover compost with a 6-12mm (¼”-½”) of agricultural grit.
Place these in a cold frame or similar cool, well-ventilated environment where excess rainfall cannot soak the pots.
Germination can be sporadic even with the best treatment, so leave the pots for up to two years if necessary.
Prick out seedlings into separate pots and grow on, planting them into a nursery bed once they are large enough.
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