How to Sow Tomato Seeds Indoors for Super Seedlings with Pots & Trowels

There’s nothing quite like the taste of sweet, juicy homegrown tomatoes, and the best part is that you can grow your own without needing to invest in a greenhouse – all you need to start them off is a bright, warm windowsill or a cheap propagator.

In their latest video, our friend Martin Fish of Pots & Trowels show you how to start off your tomato seeds indoors for strong, bountiful plants. You can watch the video below, or keep reading for all the tips, tricks and equipment you need to sow tomato seeds for a totally tip top tom harvest this year!

When is the best time to sow tomato seeds?

Don’t worry about if you haven’t sown your tomato seeds yet, as mid-March to early April time is an ideal time to start your seeds indoors. The warmer weather and longer days means that they’ll germinate faster and your seedlings will grow into lovely short, stocky, strong plants that will be perfect for growing in the greenhouse or for planting out in the garden in May, as opposed to tall, leggy plants that can occur if you start sowing your tomatoes too early when there’s not as much warmth.

In the video, Martin is sowing the standard variety Tigerella and cherry variety Tumbling Tom from our friends at Mr Fothergill’s. Compact trailing varieties like Tumbling Tom are ideal for planting in hanging pots or baskets, so a great choice if you’re a little low on ground space. Head to the Mr Fothergill’s website to check out the full range of terrific toms they have in stock!

Top tip: Seal up any packets of opened tomato seed and keep them in a cool place, such as a fridge or cool shed, so that any leftover seeds can be saved and sown again next year.

A close up of hands holding two packets of Mr Fothergill's tomato seeds

How to sow tomato seeds indoors

What you’ll need:

  • Tomato seeds
  • Multi-purpose compost
  • Small plant pots
  • Tomato feed

Fluff up some of your compost to get plenty of air in it and get rid of all the lumps, then fill a small pot with it. Level it off by hand and give the pot a few taps on your work surface to help level out the compost. You can also use the base of another plant pot, a jam jar or similar to lightly tamp down the compost surface to create a nice level sowing surface, making sowing easier and giving all the seedlings a good fair chance to grow.

The idea is to sow the seeds so they’ve got an even amount of space, an even depth of compost and an even covering – that way, you should get an even batch of seedlings and plants as they grow on. Sow a few seeds per pot depending on how many plants you want. If you end up with any spare plants, you can always donate them to family and friends or neighbours.

A close up of some tomato seeds spread out of top of some compost in a small brown plastic plant pot, with a hand holding some more seeds in its palm

Cover your tomato seeds with a fine, even layer of compost (around 3-4mm or ¼ inch) using your hand, or use a sieve for a really fine covering. You can always practice sprinkling the compost on a nearby surface with your hand to get the coverage right first. It’s important to get an even coverage as you want the seedlings to all start coming up at the same time. Cover until all the seeds have disappeared and then label your pots right away (especially if you’re sowing several different types!) so you can remember which pot is which.

Tomato seeds ideally need a temperature between 15-20° to germinate, so your pots need either a propagator or a warm windowsill to give them the warmth they need to get started. There’s plenty of cheap options out there for electric propagators if you don’t have a warm place to put them, or if you have a warm room or sunny windowsill then an unheated propagator is a good way to go.

Give your pots a light watering and then you shouldn’t need to water them again until you start to see some growth, as there should be sufficient watering in there from the first watering to aid germination. You can water them again once your seeds have germinated and the top later of compost has dried out. Don’t overwater your pots as this will create wet, cold conditions that are likely to lead your seedlings to rot off.

A small brown plant pot containing tomato seeds sat in a propagator, being watered with a green watering can

In no time you’ll get lovely strong plants and a wonderful crop of tasty tomatoes later on in the summer!

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