Tips on sowing tomato seeds

 In Gardening, Plant Propagation, Sowing, Vegetables

Tips on Sowing Tomato Seeds

Sowing tomato seeds to raise your own tomato plants is not difficult but there are a few key points that need to be taken into consideration. I’d love to share with you a few tips on sowing tomato seeds.

There’s a handful of vegetables that I’d never be without. These are the ones that yield well and often taste better when you grow your own. Runner beans, varieties of salad leaves, courgettes, spinach and of course the tomato; these are the ones I go for!

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First flower open on first truss – the perfect stage to plant out

Naturally you might choose to buy a tomato plant in a 9 cm pot for planting out but this tends to restrict your choice of variety. In any case I would suggest that you grow it on before planting out. I have found that the ideal stage is when the first flower truss is well developed and the first flower is already open. If you plant earlier then there is a risk that the first truss will be blind as it often fails to set fruit.

This year I’m sowing tomato seeds of my old favourite for flavour ‘F1 Sungold’ again. I’ve been tempted to sow some ‘Rosella’ too as I’ve heard that it’s good and tasty. I believe that F1 Sungold is far better than the number one selling cherry tomato variety ‘Gardeners Delight’.


Firstly, if you haven’t got new containers, make certain that the pots or seed trays that you are use are spotlessly clean. Very hot water will do this.

Compost media

Equally you must use fresh new compost when sowing tomato seeds. This could be seed compost or multi-purpose compost but should be this year’s stock and not some discounted bags left from last year!

Here’s how to do it

Loosely fill your container to the lip and strike off any excess. Then firm the compost down so that you can cover the seeds with 6 mm (1/4”) of compost and still have enough room to water the top of the container. This depth of covering has a purpose more significant than with other seeds. Tomatoes are prone to many virus diseases and a few of those can be carried on the seed coat. With this depth of compost, the seed coat is left in the seed compost as the seedling emerges. And so the possibility of the seedling becoming infected from the seed coat is reduced.

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F1 Sungold tomato plants

It’s important when sowing tomato seeds to sow thinly. This allows plenty of space between each seedling and encourages strong healthy plants.

How to wet the compost

Once sown, I like to moisten containers by standing them in a tray of water. This allows the whole of the compost to become wet without disturbance to the surface. Naturally I use only fresh tepid water for this.


Light is not needed to germinate tomato seed but warmth is. A temperature of 18-21 C (65-70 F) is ideal and this can be in the airing cupboard. However, as soon as the first seedling emerges it needs good light. Germination takes 8-10 days.

My tomato plants are destined to be grown in an unheated poly-tunnel. If you intend growing tomatoes outside I would suggest waiting until April for sowing tomato seeds.

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Germinating tomato seedlings on a windowsill

Transplanting – a k a ‘pricking out’

Once germinated and the strap-like seed leaves have fully expanded, waste no time in transplanting each to a 9 cm pot filled with potting compost. Never handle the delicate seedlings by their stems which easily bruise. Always handle each by a seed leaf which is in any case quickly replaced by true leaves. Use a ‘dibber’ [or pencil] to ease each seedling out and to carefully replant them.

If you’re into plant propagation you might like to read about taking late summer cuttings here .

You might like to try taking root cuttings or perhaps hardwood cuttings.

There’s some good general advice on seed sowing on the RHS website here

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