How To Sow Tomato Seeds For Maximum Germination

basket of homegrown tomatoes

Tomatoes are my all time favourite food to eat and to grow. And given how rubbish the supermarket ‘versions’ can be, I suspect that they are high on your list too.

You can grow tomatoes from at home by sowing tomato seeds shallowly into pots or cells filled with a loose, well-draining seed starting mix, and then covering them to maintain humidity and leaving them in a warm location for one to two weeks to germinate.

To successfully sow tomato seeds you’ll need to:

  1. Find a suitable container
  2. Fill it with a seed starting mix
  3. Make a small hole in the soil, about 1/4 inch deep into the surface
  4. Place seed in the hole and cover with more mix
  5. Water the soil by bottom watering
  6. Cover to maintain humidity and place in a warm location

In this article and in the video below, I’ll guide you through each step so that you can get both fast germination and the best germination rates possible for your seeds.

YouTube Video: How To Sow Tomato Seeds To Maximise Germination

When To Sow Tomato Seeds

The recommended months for sowing tomato seeds is usually February through to early April, depending on your region. In Italy it is traditional to sow seeds on valentine’s day and in the East of England, I’ve had my best harvests sowing seeds on the 15th of February.

However if you have strong enough grow lights for tomato seedlings and the time to care for them, you could sow seeds as early as January or maybe even December in relatively warm years.

Should I Soak My Seeds?

Soaking tomato seeds in tea is said to speed-up germination by both enabling the seeds to absorb water faster and by degrading the seed coat through fermentation and chemical reactions. However results are mixed and some people find using the paper towel method has the fastest germination times.

While this step is optional and the results inconclusive, I still soak my tomato seeds in black tea for 24-48 hours before sowing them into a seed starting mix. I will test this myself and update this article with my own results.

What Soil Is Best For Germinating Tomato Seeds?

Tomato seeds require constant moisture as they need to increase their water content from dry to 80% before they will germinate. However they also need good airflow and oxygen to prevent damping off. Therefore a loose, free-draining, water-retentive seed mix is ideal for sowing tomato seeds.

You could buy a seed starting mix, designed to be more hospitable to seeds, or you could use something like coconut coir, which keeps moisture without restricting airflow but doesn’t contain any nutrition and will require you to perform an early transplant.

A blend of coconut coir, an organic seed compost and perlite in equal parts is my standard seed starting mix and I tend to find near-perfect germination and no issues with damping off. Read this article for an explanation of why this mix is best and results of my own germination tests.

my best seed starting mix being measured out and blended
I make my own blend of seed starting mix which I think has zero drawbacks and gets basically perfect germination every time.

What Container Should I Use For Sowing Tomato Seeds?

You want to use a small container when sowing tomato seeds as the seeds are small, not sensitive to root disturbance and, crucially, tomato seedlings suffer in waterlogged soil. Therefore a smaller pot where the water can drain or be taken-up by the plant is ideal. You can use:

  • Pots – ideally less than 5 centimetres (two inches) across so that moisture levels can be controlled.
  • Propagator Cells – a plastic container with multiple ‘cells’ with a drainage hole arranged in a grid, often with an adjustable lid for controlling humidity.
  • Plug Trays – Commercial cell trays designed for space-efficient growing of seedlings. They only contain a small amount of soil so will need to be transplanted sooner than with pots or wider cells.
  • Paper Towels – An alternative method for germination that prevents soil-borne diseases and limits anaerobic conditions that might hinder germination. There is no soil and not much light here so seeds will need to be planted as soon as they spout.
  • Egg Cartons and Yogurt Pots – Home-gardeners have a habit of collecting used cardboard and plastic food containers for holding soil and growing seedlings in. With correct drainage these are cheap alternatives to the above options.
rows of 5cm pots filled with tomato seeds
I like to use little 5cm pots for my tomato seedlings for the first month or two

How Deep Should I Sow Tomato Seeds?

Tomato seeds are very small which means that they don’t need to be planted very deeply. In fact, if they are planted too deeply you will start to see germination rates diminish. As a rough guide, sow seeds roughly twice as a deep as they are wide.

You should sow tomato seeds half a centimetre (a quarter of a inch) below the surface to ensure that the seedling can emerge from the soil. If you sow them deeper, the seedling may run out of energy before it reaches the surface and start to collect it’s own energy via photosynthesis.

I like to fill each container with my seed starting mix and then use my finger to make a small depression in the soil. I then place the pre-soaked seeds in each of the shallows holes and then I sprinkle some more seed mix on top. I then bottom water to ensure that the seed isn’t disturbed and remains near the surface.

Sowing a tomato seed into a module cell tray filled with seed starting mix
Sow tomato seeds one seed per cell or pot, only a fingernail’s depth from the surface

How Many Seeds Should I Sow In Each Pot?

Sow one tomato seed per cell or per pot as you should get high germination rates with tomato seeds. By sowing one seed per container, you avoid having to thin out seedlings later and, if you are using a large enough pot, you might even be able to avoid transplanting too.

Where Is The Best Place To Germinate Tomato Seeds?

Tomato seeds will germinate fastest when placed in a warm location as they require heat to germinate. You can purchase a heat mat to control the soil temperature, but a warm shelf above a radiator or a boiler flue or an airing cupboard will be sufficient. Tomato seeds do not need light to germinate.

All seeds require moisture to germinate which means that you need to prevent the soil from drying out. To trap humidity and maintain soil moisture, you can use a propagator lid or humidity dome which is a plastic cover that you place over the top of a seed tray. They may be provided as part of a kit. Alternatively you can wrap the individual pots or trays with cling film.

How Long Do Tomato Seeds Take To Germinate?

Tomato seeds can take up to two weeks to germinate but this is highly dependent on the variety. If you soak seeds and place them in a warm location and maintain the ideal humidity levels, you may see germination in as little as three or four days.

If you want to speed up the process, see this article about all of the ways that you can speed up germination.

tomato seedlings in a cell tray under grow lights
In a week or two, you should see small seedlings starting to germinate. Put them in a bright position or use artificial lights to keep them healthy. A month later, you can still see how leaving seedlings in darkness for a day or two late can cause legginess in your seedlings. See the difference in the seedling that germinated late (front).

What To Do After Your Seeds Have Germinated

Once seeds germinate, remove any cover and provide them with as much light as possible. Tomatoes are warm climate crops that require good lighting and by providing artificial heat, you are germinating them early. You should place seeds on a sunny windowsill and consider using supplemental lighting.

Of course, if you are sowing your seeds early and trying to get a head start on the season then it’s very likely that there still isn’t enough natural daylight to prevent your tomato seedlings from going leggy.

To prevent this, many gardeners turn to grow lights to provide supplemental lighting during the winter months and quite often end up buying cheap ones on Amazon. But are cheap grow lights bright enough to grow tomato seedlings? And how much light do tomato seedlings really need? It turns out, their light requirements actually depend on many variables, including the variety that you are growing. Find out more in the article below.

Happy Gardening!

Similar Posts

Leave a Reply

Your email address will not be published. Required fields are marked *