Growing from seed

Bill Brett | 25 October, 2021

            Growing seedlings from seeds nz

At a Glance

  • Warm, sheltered site.
  • Quality seed raising mix.
  • Quality fresh seeds 
  • Keep damp but not wet 

The seed.

Start with good seed. We recommend checking out the hybrid varieties in Yates, McGregors, Mr Fothergills or  ican range.  Mail order is good for the keen gardener as there is a larger range to choose from with much more information.  Egmont Seed Company has the best range of hybrids.  Kings Seeds have a large range with less hybrids but many unusual novelty types.

What is a hybrid?

A hybrid is created when the pollen from one variety of plant is used to pollinate a different variety of the same plant. Breeders 'cross pollinate' in order to try and combine different positive attributes into the same plant. Hybrids are usually bred for disease resistance, taste and performance. The results are more certain and more uniform. One thing to be aware of if you like to save seeds from your plants to grow next year. Due to the amount of cross pollination, seeds from hybrids typically don't produce true to type so variations will occur. You will need to buy hybrid seed to get the same results.

Always use fresh seed as some seeds (especially parsnip, lettuce, onion, leeks) have a short life once the foil sachet packet is opened. Ideally you should use the seeds in the same season the packet is opened. The seed in unopened foil sachets should remain viable for some years. Keep seed in a cool dry place. A sealed glass jar in a dark cupboard is best. Choose varieties to suit your area and the season. 

Sowing seed  

A few species such as carrots, parsnips, turnips, peas and beans, are best sown directly in the soil. This is because they are either a root crop or they dislike being disturbed. Most others are best sown in a tray to germinate and then transplanted out into the soil as young plants.

Raising young plants in punnets or small pots also saves time allowing better use of the garden space. 

Raising seed in trays, punnets or pots

Use a quality seed raising mix such as Yates Black Magic. If re-using old trays punnets or pots, ensure they have been washed thoroughly in order to remove all traces of soil which could be carrying soil fungal diseases that attack germinating seeds.

Why use seed raising mix?

Seed raising mix is a really fine blend that allows drainage while holding onto enough moisture to stop the seeds drying out. The fine particle size allows the delicate roots to easily push their way through as they develop.

  • Fill the containers with seed raising mix, water, and allow to drain for 30 minutes or so.
  • Some gardeners prefer to sow 2 –3 seeds in each cell of the punnet or pot, and then thin out to 1 per cell / pot after germination.                                                   
  • Other gardeners prefer to sow a number of seeds in a punnet/ pot / or tray and when they have germinated and have 2 true leaves (the next two to appear after the 2 seed leaves), they are carefully ‘pricked out’  into punnets, pots, or spaced out in a tray.  

With either technique, sow the seed to a depth of 2-3 times it’s thickness, or place on the surface and cover 2-3 times it’s thickness with seed raising mix.

It is important that the mix in the sown punnets / trays, remains damp but not wet, until germination is complete, which takes from 1—3 weeks for most species. This is best achieved by placing in a small glass or polythene covered cloche, or by covering with a sheet of glass. A sheet of newspaper in addition will also help. 

Place in a warm sunny place in winter / early spring or in a shady place in summer

As soon as germination is complete, remove glass or cover and allow ventilation.(In early spring cover at night). Keep moist but not wet, and ensure the young seedlings have good light.   

After another 2—3 weeks the young seedlings will be ready for transplanting into the garden.

Sowing direct into the soil

This is the method for root vegetables such as carrots, parsnips, radish, beetroot, and swedes,  as well as peas, and beans. Other large seeds such as cucurbit family (cucumbers, pumpkins, squashes melons etc...) and sweet corn are also often sown direct in the soil where they are to grow.

Sowing seed direct in the soil can be difficult in old diseased soils, or clay soils, where drainage is poor.

Therefore start by ensuring the soil has lots of compost added and is free draining.

 Another good idea is to create a shallow furrow about 30mm deep in the row where the seed is to be sown. Fill this furrow with seed raising mix.

Sow the seeds at a spacing as advised on the packet and cover. Firm the surface gently to ensure seed to soil contact which also minimises drying out.

Early in the season in colder districts it is common to cover with a cloche.

Troubleshooting if seeds don’t germinate or are deformed

  1. Too wet—prevents oxygen getting to the seed, and increases fungal rots
  2. Too dry— seeds part-germinate and then die. 
  3. Too cold—most seeds need moderate to warm temperature to germinate.
  4. Too hot—direct hot summer sun will kill germinating seeds.
  5. Planting too deep—is likely to be both too cold and too wet. 
  6. Planting too shallow—seeds likely to dry out and die during germination.
  7. Seed mix / soil too loose—insufficient moisture supply to the seed.
  8. Seed mix too firm—creates water-logging and stops oxygen getting to the seed.
  9. Presence of soil fungal diseases—common in old gardens, dirty containers, or old used potting mix.
  10. Slugs and snails—will commonly attack seedlings as they germinate.
  11. Birds / cats / dogs scratch out seeds and young seedlings.
  12. Seeds germinate but are ‘stretched’ with long weak white stems—insufficient light or sown too thick.
  13. Fertiliser burn—don’t apply concentrated soluble fertiliser close to seedlings.
  14. Seed viability—use fresh seed. If the foil packet has been open for more than a year, some seeds, especially lettuce, parsnips, celery, leeks and onions will lose viability.
    For more details, step by step photos, and a list of our recommended varieties become a subscriber to  Pro Advice