Some very fine seeds, (eg. some petunias) have been ‘pelletised’, coated with a layer of inert material to make them easier to handle. These should be watered more frequently than uncoated seeds.
Sow large seeds, such as sweet peas, sweet corn, peas, beans and broad beans, into damp soil. Avoid watering while the soil remains moist or until the seedlings emerge. Do not pre-soak these seeds.
Keep soil or seed raising mix moist for slower germinating seeds (such as pansies which may take 21-28 days).
After seedlings have emerged, water thoroughly but less frequently to encourage the development of good, strong roots.
Soil temperature is critically important for successful germination.
Some seeds need a cool-cold soil to germinate.
Others need a soil temperature of at least 25°C for best results.
Soil should be consistently warm before sowing warm season varieties direct in the garden.
Cool soils cause many failures with seeds of summer plants (such as tomatoes) that are sown in early spring.
Seeds can be sown in pots in a warm, sheltered spot and transplanted out into the garden when conditions are more favourable.
A hint for raising temperature-sensitive seeds, such as petunias, in early spring is to sow into a 15cm diameter pot, water well and enclose the pot in a plastic bag that is sealed around the rim. Place the pot on a gentle source of heat – such as a hot water tank or a refrigerator. As soon as seedlings appear, remove the plastic bag and harden off seedlings outdoors.