Propagating from seed

17 JUL 2023

Growing plants from seeds is an important skill to master for any gardener as home-grown seedlings can be cheaper and healthier than plants sold in nurseries. Seeds can be obtained from our local nurseries or supermarkets, or even harvested from your own plants!

  • Seed packets come with for useful information on growing plants, including:

    • The seed expiry date
    • Recommended sowing depth, distance, and harvest cycle

    This information is important for gardeners to take note of as it helps with sowing and harvest planning, and managing the spacing of plants. Planning when to sow seeds and where immediately after buying seed packets will ensure that you use them before they expire!


    Thrifty gardeners often harvest their own seeds from existing plants in their garden. As a rule of thumb, mature fruits will have viable seeds that can be dried and stored in a cool, dry place for up to 6 months for planting.

    Some common plants that have easily harvestable seeds include:

    If the ripe seeds are not harvested in time or exposed to rain and humidity, they may start to sprout, or rot.

    It is a good practice to use seeds as soon as they are bought or harvested as germination rates will decrease over time. Unused seeds should be stored in air-tight containers, and placed in cool, dry areas such as a refrigerator to extend its shelf life for up to 6 months.

  • Seedlings and seeds are vulnerable to pathogens and disease. They are also prone to rot if they are left sitting in water for too long. You can make your own well-draining seed-starting mix with sterile soil amendments. Pure cocopeat, pure perlite, or an equal mix of cocopeat and perlite are good mixes for starting seeds.


  • Sowing seeds individually in seed trays or pots is a good practice as seedlings will not compete, and it is easier to observe which seedlings are stronger and therefore easier to grow.

    Seedling trays or pots can be filled with sterile seed-starting mixes, which prevents pathogens like fungi and bacteria from killing vulnerable seedlings. The trays or pots can also be kept in a sheltered propagation area to keep seedlings away from pests and harsh weather.

    Seedling trays are for smaller plants and smaller seeds, while seedling pots are for larger plants with larger seeds. For example, tomatoes do well in seedling trays as their seeds are only a few millimeters across and have sprouts that are less than 5cm high, while pumpkins have large seeds up to 1.5cm across and sprouts that can quickly reach 10cm in height in a few days. A good rule of thumb is that seeds less than 0.5cm can be started in seedling trays, while seeds larger than 0.5cm can be started in seedling pots.

    Here is how you can start seedlings in trays and pots:

    1. Get a seedling tray or seedling pots. Seedling trays and pots should allow water to drain out. You can buy a commercial seedling tray, or make your own using a cardboard or plastic egg tray with holes poked at the bottom. Seedling pots can be made out of toilet paper rolls, or small plastic pots no deeper than 10cm.
    2. Fill the seedling tray or pot with potting or seed-starting mix. Ensure that you use new sterile soil or soil amendments to minimize chances of fungi and bacteria from killing your seedlings.
    3. Sprinkle 2-3 seeds into each cell or pot evenly.
    4. Cover the seedlings with a thin layer of potting or seed-starting mix.
    5. Water the soil thoroughly with a fine spray.
    6. If more than one seed sprouts per cell or pot, remove the less healthy seedlings to leave one seedling per cell.
    7. When seedlings have 4-8 leaves, they are ready for transplanting.

    This method of sowing and transplanting seeds is particularly good for the following plants:


  • Seeds sown directly into bigger pots, true ground or wherever they are meant to grow permanently will grow quickly and will not suffer from transplanting shock like seedlings in seed trays or pots. This also a good way for growing plants with large seeds bigger than 0.5cm as these seedlings often get constricted by small seedling trays. It is also a good way to grow plants that can grow in tight clusters or as a ground cover. However, seedlings sown this way will have to compete with weeds, and are vulnerable to pests like snails and slugs, harsh sun, and heavy rain. These seedlings may need to be protected with netting or a cloche to survive. The large amount of unsterilised soil also exposes seedlings to pathogens like fungi or bacteria, which can kill them.

    How to sow seeds directly:

    1. Make sure that the new planting area is large enough with the appropriate soil depth for the fully-grown plant. Prepare the soil and remove weeds and other debris from the planting area.
    2. Make a shallow groove in the soil along the length of your planting space.
    3. Sprinkle small seeds or space out large seeds into the groove evenly
    4. Fill the groove with sterile potting or seedling mix.
    5. Water the soil thoroughly with a fine spray.
    6. After sowing, install with netting or cloches to protect the seedlings from rain and pests.
    7. Thin seedlings according to their final planting space when they have 4 or more leaves.

    This method of sowing seeds is particularly good for the following plants: