How Do I Grow Tomatoes from seed?

Well, tomatoes are reasonably easy to grow, but there are a few important things to remember.

Tomato seeds need warmth to germinate. That means the SOIL temperature needs to be 20C or warmer all day and night.

Just think about that before you plant your seeds. 20 degrees C, every day and it is the soil temperature we are talking about not air temperature.

totem tomatoes

If it is cooler than that, they may still germinate but they will take a lot longer.

Here are the scientific facts about tomato germination… if the SOIL temperature is 10C or below your tomato seeds won’t germinate at all. They will just sit there.

If the soil temperature is just above 10C, it might take up  to 6 weeks for the seeds to germinate and, of course, that will finally start to happen because the days are getting warmer and longer.

If the temperature in the soil is 15C they will germinate but might take 2-3 weeks to do so.

If the soil temperature is between 20-25 C then you will get the best germination rates and it might only take a few days to a week.

But once the soil temperature starts going over 30C the germination rate slows again and germination time increases and then stops once you get to 40C.

As you can see soil temperature is critical and this is why it is far better to raise many seeds like tomatoes on a heat mat.

This same pattern repeats with all seed varieties, they just have different temperature ranges.

This is what happens in nature. At the end of the season the tomato falls on the ground and sits there rotting. Nothing happens until it gets warm enough. The same goes for the tomatoes that you plant. They need warmth and will resist germinating until they get the consistent warmth THEY want.

So many gardeners will blame seeds for their own impatience but in my experience over 40 years, it is the gardener who is the problem, not the seeds.

Let me give you an example…

Most tomato seeds have a tested germination rate of around 90%. That means that for every 10 seeds you plant, 9 will grow. If you plant ten seeds, it is mathematically VERY unlikely that all ten seeds will not germinate. It is VERY likely that you, the gardener, is doing something wrong. And usually it is most likely the temperature is not right.

How do you get around this?

Use a heat mat! I always use a heat mat to germinate tomato and chilli seeds. It gives the seeds a consistent warm temperature and even though I live in Tasmania I can germinate tomato and chilli seeds even in the middle of winter. If you don’t have a heat mat, try a warm window sill. Or if you have a hot water heater inside or in the garage, place your seed tray on top of that.

All you need to germinate tomatoes is warmth, moist but not wet soil, and good potting mix. I prefer to use a good see raising mix rather than potting mix as they tend to have no fungus gnats in the product.


Here is a rough guide and remember, if you start your seeds early, they need to be in a warm position.

A) If you live in Sydney, or a climate with similar conditions…

You can plant tomato seeds in Sydney in August and you can plant every month until March.


In Sydney you can plant tomatoes in August. In Sydney you can plant tomatoes in September. In Sydney you can plant tomatoes in October. In Sydney you can plant tomatoes in November. In Sydney you can plant tomatoes in December. In Sydney you can plant tomatoes in January. In Sydney you can plant tomatoes in February. In Sydney you can plant tomatoes in March. Sorry, I just had to spell that out in simple English.

And yet most people only plant in August and September. Don’t plant all your tomatoes at once. Plant a few early, then a few more every couple of months so you get new vigorous tomato plants until winter.

B) If you live in Adelaide or Melbourne, or a climate with similar conditions, you can plant tomatoes from September to February.

Yes, you can still plant tomatoes in Melbourne after Christmas, and yet I get customers who tell me they have to plant their seeds in September otherwise it is too late! Amazing.

C) If you live in Tasmania, or a climate with similar conditions, you can plant your tomato seeds from September to December.

All the above rules come with one big BUT!

Tomatoes don’t like frost. Frost kills tomato plants. So, if there is still a chance of frost in your area, then plant your seeds indoors, and raise the seedlings indoors until the last frost date is past.

And a quick word on potting mix… tests of different potting mixes have shown that the potting mix DOES matter. Some even kill off your seedlings they are so poor in quality.

Only buy a potting mix with a Red or Black tick on the front. But remember, that if you grow a tomato in a container, it will exhaust the nutrients in the potting mix faster. If the potting mix says it fertilises for 6 months, and you grow a big plant in a small container, you will find the nutrients are exhausted after only a few months. Then you will need to fertilise regularly to get the maximum crop from your plant.

To see our range of popular and exotic tomato seeds, go to our shop here…

Happy growing!

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