About seeds……….and plants | Understanding helps germination and success!
Some seeds have hard seed coats which prevent moisture being absorbed by the seed. All that is needed is for the outer surface to be scratched or abraided to allow water to pass through.
This can be achieved by chipping the seed with a sharp knife at a part furthest away from the ‘eye’, or by rubbing lightly with sandpaper
Soaking is beneficial in two ways; it can soften a hard seed coat and also leach out any chemical inhibitors in the seed which may prevent germination.
24 hours in water which starts off hand hot is usually sufficient.
If soaking for longer the water should be changed daily.
Seeds of some species swell up when they are soaked.
If some seeds of a batch do swell within 24 hours they should be planted immediately.
As each seed swells it should be removed and sown before it has time to dry out.
Small, Tiny and Minute seeds.
If you think that planting tiny seeds is a drama, just imagine collecting, cleaning and counting them. Throughout the site we mention seed size where it seems appropriate but to make it easier to understand, Small is the size of the comma, ‘,’ and Tiny is the size of the full stop. ‘.’ and you will have trouble seeing Minute. (eg. Irish Moss). Looks like dust really!
These seeds need to be sprinkled on the surface of your seed raise mix and left to do their own thing. Years ago, we pre-mixed the seed with talc or fine sand to make it easier to spread the seed on top of the pot, but customers were unconvinced that there actually was seed in the mix so now you must do it yourself. It does make sowing a little easier.
Stratification or cold treatment
Some seeds need a period of moisture and cold after harvest before they will germinate-usually this is necessary to either allow the embryo to mature or to break dormancy.
This period can be artificially stimulated by placing the moistened seed in a refrigerator for a certain period of time (usually 3- 5 weeks at around 6 C).
With tiny seeds it is best to sow them on moistened sand or seed raise mix, seal the container in a Polythene bag and leave everything in the refrigerator for the recommended period.
However, larger seeds can be mixed with 2-3 times their volume of damp mix, placed direct into a Polythene bag which is sealed and placed in the refrigerator.
Look at seeds from time to time. The seeds must be moist whilst being pre-chilled, but it doesn’t usually benefit them to be actually in water or at temperatures below freezing.
Light also seems to be beneficial after pre-chilling and so pre-chilled seeds should have only the lightest covering of mix over them, if any is required, and the seed trays etc. should be in the light and not covered with brown paper etc.
Some seeds have a combination of dormancy’s and each one has to be broken in turn and in the right sequence before germination can take place; The first period, during which the root develops and then a three month chilling to break dormancy of the shoots, before the seedling actually emerges.
The seeds are best sown in containers of free draining seed raising mix and placed in a cold frame or plunged up to their rim outdoors in a shaded part of the garden, preferably on the north side of the house avoiding cold drying winds and strong sun. Recent tests show that much of the beneficial effects of pre-chilling are lost if the seed is not exposed to light immediately afterwards. We therefore recommend sowing the seeds very close to the surface of the soil and covering the container with a sheet of glass.
An alternative method especially with larger seeds, is to sow the seed in a well prepared ground, cover with a jam jar and press this down well into the soil so that the seeds are enclosed and safe from predators, drying out etc.
A steady temperature between these limits is recommended-fluctuating temperatures can damage a seedling in its critical early stages.
Most reputable seed raising mixes will be quite adequate.
On no account should potting composts, which have additional fertilizers, be used.
The size of the seed is usually your indication. Three times the height of the seed is usually maximum.
If in doubt sow shallowly, but always ensure that the seed mix surface is damp.
The previous data has been adapted from the Successful Seed Raising Guide. This guide is out of print.