Successful Seed Raising
The three important factors to be considered when germinating seeds are sowing depth, soil moisture and soil temperature.
- 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. Peas and beans, for example, may be planted 25mm deep.
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, coleus, feverfew, 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.
- 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.
- 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 the garden
Larger seeds are usually the most suitable for direct sowing.
- Vegetable seed examples are beans, peas, sweetcorn, pumpkins and cucumbers
- 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.
- If soil is heavy and holds water, put a layer of Yates Seed Raising Mix where the seeds are to be sown.
- Mark out shallow rows to the appropriate depth with the edge of a flat board.
- Scatter seed thinly along the rows and cover with seed raising mix.
- Water well with a fine, gentle spray.
Sowing into containers
- Use seed raising mix rather than garden soil.
- Most potting mixes are unsuitable, but may be used under a 3cm layer of seed raising mix.
- Pre-moisten seed raising mix by putting it into a plastic bag, adding sufficient water, and shaking or tumbling vigorously.
- Check moisture level of the mix regularly – don’t let it dry out.
- Keep pots in a protected spot (a well-lit, shaded position is best).
- Seeds can be started indoors but seedlings may become thin and leggy if they’re left too long indoors.
- As seedlings emerge, harden them off by gradually increasing their exposure to sun and heat.
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