Tomatoes are the UK’s favourite summer vegetable, although technically it is a fruit. I used to buy juvenile plants later in the season to grow on, but now I grow mine from seed as it’s so simple to start them off on the kitchen windowsill.

There are many different varieties of tomato to grow, such as cherry, plum and beefsteak. Each variety has its own distinctive shaped, flavour and culinary use.

Tomatoes are split into two main growing types: bush (determinate) and cordon (indeterminate). Bush types are usually planted in pots or hanging baskets and their stems trail around the edge.

Cordon types are trained to grow tall and are supported by a cane or stake and will need the side shoots removed. Bush tomatoes don’t need staking.

When is the best time to sow tomato seeds?

Check the seed packet, but ideally you can start sowing in January until late-March.

  1. Fill a small pot with peat free moist seed compost and remove any lumps.
  2. Sow a sprinkling of seeds over the top – but don’t overcrowd them as the seedlings will compete for food and light. Also, it can lead to fungal diseases if there are too many seedlings.
  3. Top with a thin layer of compost or vermiculite. Tomato seeds don’t like to be too deep.
  4. Place on a warm and bright windowsill or in a propagator.

The seeds should germinate in 7-14 days. Remember to keep the compost damp during this time. Ideally water from beneath and let the compost soak up the water.

When the seedlings are around 3cm tall, you can pot them on into larger pots. Use a normal compost or one especially for tomatoes. Keep them warm (but not hot) and protected. If you’re growing cordon type of tomato, you will probably want to stake the plants with a bamboo skewer and use soft string to tie it in.

Once all the frosts have passed (around April/May time frame) you can plant outside in a sunny spot on the patio. Obviously if you are lucky enough to have a greenhouse, you can grow them on in there.

Water regularly to keep the compost evenly moist. Fluctuating moisture levels can cause the fruit to split. Feed every 10-14 days with a balanced liquid fertiliser, changing to a high potash one once the first fruits start to set.

Tomato Seed Kit by Border in a Box

I have created a seed growing kit which contains – a packet of “Gardeners Delight” tomato seeds, 3 x coir pellets, 1 x sowing guide.

Tomato Gardeners Delight (indeterminate)
Sow indoors January to April
Sow outdoors April to May
Harvest June to October
The seed packets contain around 50 seeds.

The coir pellets included in the kit have a type of ‘netting’ around them to keep the compost in one place, so no need to buy pots or seed trays to germinate your seeds with this kit.

  • Place the coir pellets on a waterproof surface – I’ve used a small melamine tray
  • Add water and watch them expand – this takes around 5-10 minutes
  • Add two tomato seeds per pellet/disc, cover over. Keep moist.
  • They will take 7-14 days to germinate. Remove the weakest seedling out of the two.
  • Once large enough, and frosts have gone, you can plant the whole compost & seedling direct into a growbag or large pot outside on the patio in the sunshine. Remember to add drainage to the pot by adding broken crocks to the base of the pot. Also add a bamboo cane (or stake) and tie in the tomato stem with twine (you will need to do this again as the plant grows taller).
  • Water regularly, but when tomatoes appear, don’t over water as this can split the fruit. Try and keep the compost evenly moist.
  • To boost fruiting, especially with plants in containers, feed every 10–14 days with a high potassium liquid fertiliser once the first fruits start to swell. I use Tomorite, but this year, I’m going to use an organic feed by Lou’s Poo’s (more info click here Lou’s Poo’s Organic Feed )

I’ve placed my coir seed pods onto the melamine tray and will place on the kitchen windowsill until they germinate and will keep watered (dont let the coir dry out).

coir disk with water

coir disk with tomato seeds

tomato seedling

Tomatoes taste much nicer if they’re grown in full sun. Windowsill gardening is a lovely project to do with the kids too and a great way to start their interest in growing their own food.

If you would like to buy a kit to get started, here is the link