IN BLOOM: Petunia's are one of the many plants that need light for successful seeding and germination to occur.
IN BLOOM: Petunia's are one of the many plants that need light for successful seeding and germination to occur.

Sowing your seeds: important factors for germination

WHEN sowing seeds in your garden, keep these three important factors for germination in mind.


  • Depends on the size of the seed.
  • Fine seed should be barely covered.
  • Medium-sized seed may be planted to a depth of about 6mm.
  • Larger seeds are planted more deeply.

Seeds that need light

  • Some tiny seeds need to be contacted by light for germination to occur. Examples are begonias, impatiens, petunias, primulas and coleus.
  • Press these into the surface of moist seed raising mix.
  • Cover with plastic wrap or glass.
  • Keep in bright shade.
  • Water by misting with fine spray or immersing the base of the container in a tray of water.
  • Varieties: ageratum, alyssum, antirrhinum, aquilegia, begonia, campanula, impatiens, petunia, primula, salvia, stock, lettuce.

Seeds that need dark

  • Some seeds need to be totally protected from light. Examples are violas, pansies and nasturtiums.
  • Cover with a sheet of newspaper or cardboard. Remove after germination.
  • Varieties: calendula, cornflower, delphinium, forget-me-not, gazania, pansy, schizanthus, sweet pea, verbena, viola, coriander.


Seeds have differing moisture requirements.

  • 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.
  • 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.


  • 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.


  • As soon as seedlings have emerged begin fertilising every week with half strength Thrive Soluble Plant Food. Don't apply to dry soil or mix.
  • Once plants are established they can be fed fortnightly at regular strength.

Sowing direct into soil

Larger seeds are usually the most suitable for direct sowing.

  • Flower seed examples are nasturtiums, marigolds, sweet peas and zinnias.
  • Prepare the soil by mixing in some well-aged compost or manure.
  • Add some Thrive Granular All Purpose plant food.
  • Dig well so that the soil ends up with a fine, crumbly structure.
  • Scatter seed thinly along the rows and cover with seed raising mix.
  • Water well with a fine, gentle spray.





For further information,

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