Growing Tomatoes from Seed
When to sow tomato seeds
Sowing tomato seeds is best done at the following times
- In a heated propagator like our Vitopod heated electric propagator or heated greenhouse - sow January to early February
- In an unheated propagator or unheated greenhouse - sow late February to early March
- Outdoors - sow late March to early April
1: Sow the tomato seeds
- Fill a seed tray with compost (any multi-purpose compost) and flatten the compost down lightly.
- Place seeds on the surface of the compost, space the seeds evenly and sow a few more than you need. Cover the seeds with approx. 0.5 to 1cm of compost.
- Water the compost so that it is damp but not saturated.
- If you have a propagator put the seed tray in the propagator and put the lid on.
- Put the seed tray or propagator in a warm place away from direct sunlight. The room needs to be a minimum of 18°C.
2: Care for the seedlings
- Day 17 -28: Seedlings should appear but some varieties can take up to 28 days to germinate – see your seed packet for details.
- Once the seedlings have appeared move the propagator/seed trays to a bright, warm part of the house, a windowsill is ideal. Keep the compost moist, but not wet. If you are using a propagator lid remove the lid when all seedlings have appeared.
3: Transfer to pots
Day 50 -60: Seedlings of most varieties will be large enough to be moved into individual 3 inch pots.
- Fill a 3 inch pot with compost and use a pencil to make a hole large enough for the seedling.
- Hold the tomato seedling by its leaves and gently lever up and out of the seed tray with a dibber or pencil and lower the seedling into its new pot.
- Gently firm the compost around the plant ensuring the roots are covered and adding compost to fill the pot.
- Water the compost so it is damp but not saturated.
- Place the pots in a warm and sunny spot such as a heated greenhouse, conservatory or windowsill in a warm room.
4: Transfer to the final pot
Once the tomato plants are 6 to 8 inches tall plant them into your Quadgrow or other chosen pot between 6 and 12 inches in diameter (see seed instructions for ideal pot size). If using a Quadgrow follow the assembly instructions.
- Fill your pots with multi-purpose compost.
- Make a hole in the compost large enough for your tomato plant.
- Lever the young plant out of the 3inch pot with a pencil or dibber and carefully lower into the new pot.
- Surround the plant with compost, firming compost around the plant and add more compost to fill the pot. Water so that the compost is damp but not saturated.
If you are using a heated electric propagator, you will need to gradually wean the tomato plants off the heat of the propagator. The timing of this stage depends on the temperature conditions and whether you have a heater in your greenhouse or polytunnel - See our ‘Hardening-off’ Guide
Tomato Growing Guide
Hardening off Tomatoes
Young tomato plants need to be gradually weaned off the heat of a propagator, greenhouse or polytunnel. The timing of this stage depends on the temperature conditions and whether you have a heater in your greenhouse or polytunnel.
The weaning off period required depends on the time of sowing rather than the development stage of the plant. This is because the key is not to subject your young plants to night temperatures below 4°C without protection.
Once your plants have developed their true leaves (the leaves that are typical of the mature plant, not the two leaves that first appear) they will usually be ready to be weaned off the heat for a few days.
Gradually decrease the humidity by turning the heat down and gradually off, opening the vents and then removing the lids.
Once the plants have been in the propagator without a lid and no heat for a couple of days you can remove your plants, just keep an eye on the night temperatures.
Night Protection in an unheated polytunnel or greenhouse
If you are growing tomatoes in an unheated polytunnel or greenhouse you will need to provide protection at night until the night-time temperature in your greenhouse/polytunnel is no cooler than about 10°C.
Caring for your tomato plant
- Tomato plants can be placed outside once all risk of frost has past, but they will do better if kept in a greenhouse or indoors overnight until the summer when daytime temperatures are no lower than 17C.
- If you are using the Quadgrow keep the SmartReservoir topped-up as per the Quadgrow instructions.
- If you are growing your tomatoes in a standard pot take care not to let the plant dry out too much or to over-water. Tomatoes hate irregular watering - overwatering or sporadic watering can cause blossom end rot or cause the fruit to split - little and often is the rule here. Try to avoid watering in the evening. Tomatoes will use very little water during the night. It’s always better to water in the mornings and early afternoon.
- Unless you are growing in one of our planters and using our plant nutrients , feed your tomatoes with a general liquid fertiliser until they are established. Following that use a high potash fertiliser to encourage your tomatoes to flower and fruit.
- Keep your tomato plants weed-free and keep an eye out for the common pests.
Cordon varieties need their side-shoots removing - this involves removing the new shoots that grow between the leaf and the stem. This ensures your tomato plant puts all its energy into growing its main stem until you remove the growing tip. Take care to remove the side shoots cleanly, without leaving any stubs or damage as this will encourage fungal diseases such as botrytis.
It is easier to manage cordon varieties if you tie the plant up with string and twist the growing point around the string as the plant grows.
Pinching-out the growing tip
Usually the growing tip is pinched out when the plant reaches the desired height. Don’t leave it too late in the year before removing the growing tip as there may not be enough time to ripen off the last fruit (unless you enjoy making chutney). Leave 2 leaves above the top flowering truss when removing the growing tip. This will ensure the last tomatoes grow to full size.
Taller plants will require some removal of the lower leaves, known as deleafing, to encourage ripening of fruit. Use a sharp knife to deleaf flush with the stem. Remove leaves up to the first (lowest) truss that has ripening tomatoes on.
Harvest can begin from mid-May and continue through to October depending on where your tomatoes are grown (when using our Vivigrow planters in a greenhouse you could even still be picking in December).
- Harvest tomatoes as and when they ripen to encourage the plant to produce more tomatoes.
- Always pick the tomato with the calyx (green stalk) still attached to the tomato. There is always a knuckle between the calyx and the truss which allows you to pick the tomato easily. Leaving the calyx on the tomato will keep it fresher for longer.
- A ripening cover considerably speeds up ripening, reducing the proportion of tomatoes that will need to be picked green as the first frost approaches.
Frost and green tomatoes - See our guide to ripening green tomatoes and protecting plants from frost.
When night temperatures are below 4°C bring your young plants into the house overnight.
We find that putting the pots on a tray makes it easy to bring all the plants into the house without too much trouble.
*Do not put tomatoes outdoors until the night temperatures do not drop below 10°C. We’re in Lancashire, so for us that means late April, which would mean sowing in March.
Did you know?
Plants that receive the perfect balance of water and nutrients are healthier and stronger, helping them to have a greater resistance to pests and diseases.
Most problems occur when plants receive too much or too little water, knowing how much to provide usually involves a little guesswork and green fingers.
If you would like to grow tomatoes more successfully our Quadgrow 4x Self-watering Pots may be just what you are looking for. These 11 litre pots are the ideal size for your tomatoes and thanks to clever FeederMat powered watering, we guarantee you'll have a bumper harvest.
We grew 4 varieties, Scarlotto, San Marzano, Rosada and Sweet Million in our Quadgrow 4x Self-watering Pots and our Gardening Angel closely followed their progress.
Need more advice?
Our Gardening Angels are always on hand to help you with any questions you may have.
Simply pop us an email at firstname.lastname@example.org or give us a call on 0845 602 3774. We will have your questions answered in less than 2 working hours.