Timing is critical in growing your own flower or vegetable seedlings, so make sure that you sow seed during the right season for your area or climatic zone because temperature, day length and humidity can all have a profound effect on seed germination.
You can consult the information on each seed packet to confirm that you are sowing each plant type at the correct time of the year.
1. Write the name of the seeds, sowing date and batch code of the packet of seeds on a label. Use a waterproof pen or an ordinary pencil to ensure long term legibility. Recording the batch code allows you to inform the supplier if germination is poor or not successful at all. Read the instructions on the reverse side of the seed packet before commencing with the procedure.
2. Fill the sowing tray with seedling growing medium to about 10 to 12mm from the top. Firm down gently with a wooden “stamper” or similar flat-surfaced implement to level the sowing surface and remove any air pockets.
3. Carefully cut open the seed packet, making sure not to damage the smaller packet containing the seed that is held within.
4. Fine seed, such as the Petunia seed in the photo is best diluted with fine maize meal before sowing, in order to make it spread easily and more evenly and also to indicate where the seed is being sown. Scattering dark seeds on a dark surface means they are difficult to see.
5. Scatter the seeds evenly over the surface of the tray by gently shaking the paper packet from side to side and tilting slowly at the same time until the seed and meal mixture emerges in an even, gentle flow.
6. Once all the seed has been sown, cover with a fine layer of vermiculite or seedling growing medium. Both options are illustrated. A kitchen sieve works well; delivering a fine, even layer. If seeds are buried too deeply they will not germinate regularly and possibly not at all. A general rule of thumb is to cover them with a layer equal to the diameter of a single seed.
7. Once again use the wooden “stamper” to gently press the seeds and the covering agent into one another.
8. Place the nametag into the tray and brush off any loose particles from the rim or lip of the tray.
9. Fill a waterproof container larger than the seed tray with clean water. The depth of the water must always be about half the depth of the growing medium in the seed tray. Place the seed tray gently into the water and allow it to soak until the surface is clearly moist and damp. This takes 20 minutes or so. Remove the seed tray from the water and allow it to drain.
10. Once drained, cover the tray with a layer of plastic cling wrap. This serves to create an evenly moist, humid environment for the seeds. Place the tray in a protected, lightly shaded position to await germination. Keep a watchful eye on proceedings, removing the cling wrap as soon as the seeds start to germinate. This usually takes between 4 and 14 days, depending on the plant type. The average germination time is always specified on the seed packet.
11. The same tray of Petunia seeds 7 days after sowing showing perfect germination. As the seedlings develop, keep the tray evenly moist. Drying out can cause major fatalities. Gradually move the tray into a sunny position in order ensure strength and stability in each little seedling. Watch for slugs, snails, cutworm and damping off during this time. All of them can spell disaster.
12. When 4 to 5 proper leaves develop on each little plant, they need to be planted on into seedling punnets with individual cells. Remove each plantlet carefully with a dibble and insert into a hole made with the same implement in the punnet. Ensure that the roots are all intact and facing downwards. Firm down thoroughly. Water well, immediately after planting. Allow the seedlings to develop for 3 to 6 weeks in the punnet before planting them out into their final growing position.
13. Petunia seedlings ready for planting out into the garden. Make sure that the root ball has filled the cell. Petunias perform equally as well if planted out in bloom or whilst still green. Regular dead heading improves and prolongs their garden performance. Weekly feeding with a water soluble plant food high in potassium will make the whole process that much more successful.