Seed Germination Basicssubmitted on 27 February 2014
The main seed-sowing season will soon be upon us, and we will be hoping for a high rate of germination from our seeds, but what do seeds actually need for germination?
Each seed contains an embryo plant encased in a seedcoat for protection, along with a supply of stored food. A combination of moisture, warmth and air should start germination. Most seeds also need darkness though a few need light to germinate.
Moisture is needed to soften the seedcoat, first allowing the roots to develop and then the shoots to work their way up to the soil or compost's surface. Large amounts of water are absorbed at the start of the germination process. Some seeds, such as sweet peas, have particularly hard-coated seeds, but you can speed-up germination by chipping the coating with a sharp knife on the opposite side of the seed to the "eye".
Germination requires oxygen, so the seed compost needs to be well-drained to allow air to get to the seeds, but also needs to hold enough moisture to meet their needs.
A suitable temperature is needed to start the chemical activity within the seeds when air and moisture are present, though this temperature varies widely. Broad beans for example will germinate in an unheated greenhouse in February, while tomatoes need a temperature of about 20C. and many flower seeds need a higher temperature still. On leaving their parent plant, many seeds need a dormant period, which frequently coincides with cold weather. Some seeds benefit from chilling before planting to aid germination.
Most seeds need darkness in order to germinate, though some are happy in the light or darkness while others must have light. Unless you are told otherwise, sow your seeds at a depth that keeps them moist and allows good root development.
A seed's ability to germinate decreases with age, with onion seeds for example only being viable for one year while carrot seeds are ok for three years and cabbage seeds for 5 years.
I hope this has given you a basic introduction to what your seeds need for germination.
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