Growing seedlings indoors

Green Lifestyle magazine

Want to kickstart your summer vegie plants this year? Get them in the ground early by starting seedlings in the warmth of indoors right now.


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Winter can be a tough period for the overexcited gardener. The sun is low in the sky, the air is frosty and growth in the garden is slow. The anticipation of lush green spring gardens can get the better of us. But there’s no need to wait until the birds are chirping – the last months of winter are the perfect time to get going on your spring garden and start your seedlings indoors.

A warm house provides a controlled environment that will encourage seeds to germinate earlier than they would outdoors. This ensures your seedlings will be ready to go as soon as the weather is doing it’s thing to warm up outside, and it provides your plants with as much growing and food-producing time as possible.

Take a look at the back of the seed packet and check the temperature at which the seeds will germinate. Many spring and summer plants, including beans, zucchinis and tomatoes, need soil to be at least 20°C to germinate. Air temperature is always warmer than soil temperature.

Prepare some containers to sow your seeds in – seedling trays, reused plastic containers with drainage holes or paper seedling pots will all do the trick. Fill with a good quality seed raising mix. I like to mix up equal amounts of coco peat, sand and compost. Finer is better – some potting mixes can be too coarse for seed raising. Having some sand in the mix provides plenty of aeration. Then sow your seeds at the depth indicated (it’s usually triple the size of the seed). 

Next up, you’ll need to find a cosy place for your seedling containers. If you have a spot that captures the warmth of the winter sun really well, that may work. I don’t have this at home so tend to huddle my seedlings together in the loungeroom where they lap up the residual warmth of the fireplace. The top of a hot water heater also works well, or you could invest in a propagating heat pad.

Don’t fret if it’s dark where you choose to home your containers. Seeds don’t need light for germination – most actually prefer the dark (lettuce seeds being one exception). You just need to be sure to move them to a well-lit spot once the seeds have germinated to keep them thriving. And of course, keep them well watered with a light misting along the way!

As the weather warms up and your little seedlings continue to develop, keep an eye out for any overcrowding within each seedling space. After a couple of weeks of growing, when they’ve developed between four and six true leaves, it’s a good idea to thin them out by determining the sturdiest seedlings and carefully pulling out any of the surrounding competitors. At this stage you may also want to ‘pot on’ the strong growers into slightly larger pots to allow more room to move. When doing this, always make sure you treat them carefully and pick them up by the leaves, not by the stem which is rather fragile. Keep up their sunlight and water levels during this time.

After another couple of weeks the seedlings will be looking for more room again – so it’s time to head outside. But before transplanting them into the ground or into larger pots, they need to be ‘hardened off’ for the best chance of survival. This simply means leaving them outside to adjust to their new environment for a few days before transplanting. And then they’re ready to move.