Sowing seeds can help you to grow a large and diverse range of plants in your garden at very little expense.
Sowing from seed is the most common method but you can also collect propagating material from your own garden and friends. You can also take cuttings, divide plants and propagate by layering. The three key factors to keep in mind when germinating seeds are the sowing depth, soil moisture and soil temperature.
1. Check the size of your seed to determine sowing depth. If it’s medium sized, plant it to a depth of 6mm. If it’s fine, just barely cover it. Plant larger seeds like peas and beans more deeply at 25-30mm.
2. Seeds and light. Some seeds germinate successfully no matter how much light they receive, others have more specific requirements.
3. Some seeds need light to grow. Those that need light are likely to have tiny seeds (Begonias, Petunias and Impatiens) so ensure that you when you press the seeds into the surface of the seed raising mix, that while they are contacting the moisture, they’re also receiving some exposure to the light.
- Cover them with glass or plastic wrap and keep them in bright shade.
- Water carefully with a light misting or by immersing the tray or container.
4. Some seeds need to be protected from the light. Violas and pansies are examples of these types of seeds. You should cover these with a sheet of cardboard and newspaper and then remove this covering after germination.
5. Control the moisture level of the soil. Seeds often have different moisture requirements.
- If you are planting fine seeds, check to see if they have been coated with a layer of inert material. If they have, you will have to water them more frequently than uncoated seeds.
- You shouldn’t pre-soak larger seeds such as beans, peas and sweet corn and you will need to avoid watering them until seedlings emerge or while the soil remains moist.
6. Know the time for germination. Some seeds germinate faster than others so know when to expect seedlings from the seeds you sow. Seedlings of peas, beans, lettuce and marigold can germinate in as little as 6-10 days while slow starters like pansy, parsley and parsnip can take up to 3-4 weeks. Australian natives are often slower again. You’ll need to the soil damp not wet for this period.
7. Control the soil temperature. This is a critical factor in ensuring seedlings emerge. Most seeds will need a fairly warm temperature of around 25°C to germinate successfully, while others need a cool to cold soil.
- Ensure soil is warm before sowing summer varieties such as tomatoes in springtime.
- Heated propagators and cloches and cold frames are tools that gardeners purchase to achieve a controlled temperature. You can improvise a cloche if you don’t want to purchase one by using a clear plastic bag inside a 15cm diameter pot. Put the pot on a gentle source of heat such as a hot water tank. Remove the bag as soon as seedlings appear and harden off the seedlings outdoors.
8. Fertilise once seedings emerge. As soon as seedlings have emerged, you’ll need to fertilise every week with half-strength fertiliser. After the plants have been established, you can drop your fertilising routine to fortnightly and use a normal strength fertiliser.
9. Sowing seeds in the garden - If you are going to sow direct into the garden, large seeds are the most suitable to use (examples include beans, peas, marigolds and sweet peas).
- Prepare your soil correctly for planting. Use manure or compost as well as plant food and dig the soil well so the texture is fine and crumbly. You may need to add seed raising mix to the sowing area if the soil is very heavy and wet.
- Mark out shallow rows. To do this, you can use two canes with string between them to make a straight line. Draw a cane along the string to mark out a row.
- Plant the seeds. Scatter some seeds along the row and cover with soil/seed raising mix. Use the back of a rake to gently push down the soil.
- Water well. Spray a fine mist of water.
10. Sowing seeds in trays and containers. This method gives you maximum control over their growing conditions before planting out, which is especially useful for plants with specific needs.
- Get your tray ready. You should use seed raising mix rather than garden soil. Moisten the seed raising mix before you put it into the tray by putting it into a plastic bag, adding some water and shaking vigorously.
- Sieve seed mix into a tray. Remember to check the moisture level of the mix regularly as you do this - don’t let it dry out. Evenly sprinkle the seeds by tapping them from a folded piece of paper.
- Planting the seeds. Put a fine layer of sieved seed mix over the seeds, then a fine layer of grit. Store at a suitable temperature and label other important details like plant type and date planted so you can easily keep track.
- Removing the seeds. Once the seeds are large enough to handle (roughly when each seedling has grown three small leaves), lift them out using a widger (a double-ended stainless steel gardening tool for transplanting seedlings and inserting cuttings). Hold them by the seed leaves.
- Transfer the seedlings into pots or trays. As the seedlings emerge, you’ll harden them off by gradually increasing their exposure to sun and heat before you plant them out. You should keep pots or tray in a well-lit, shaded position. To keep animals at bay, you can place a netting over the seeds. To protect sensitive seeds against excessive moisture loss, use a sheet of glass.
- Planting out. When it comes time to plant them outdoors, be sure to plant in a sunny position, water regularly and feed it with a liquid feed that is high in nitrogen.