Tips For Tomato Seedlings

My last batch of seeds are now sown but there are still several varieties that didn’t make it to the seed tray – there’s always next season!

Seedlings at Four Weeks
Tomato Seedlings at Four Weeks.

Just in case we have another poor summer, I’m growing about 50% cherry varieties and the rest medium and beefsteak varieties. Cherry toms are the ones most likely to succeed in a poor summer.

Watering Seedlings

Seedlings up to four weeks
At this early stage it is very important not to over-water seedlings. In fact, they will develop a better root system if they are slightly under-watered and have to work hard to search for water.

Seedlings over four weeks
At four or five weeks is a good time to transplant seedlings to their own pots, or into pots if you are growing in sponges or pellets/plugs.

If you add perlite to the mix, you can water from above as there is no chance of compaction and removal of air.

If you are growing in seed compost or potting compost only, it’s a good idea to water from below. It’s also a good idea to allow compost to dry slightly to get plenty of air back into the root zone as the soil dries. Obviously, never allow soil to dry-out completely.

Over-watering will reduce air in compost, slow plant growth, root development and possibly cause root disease.

Allowing compost to dry-out a little before transplanting helps to make the soil lighter and roots less likely to break.

Feeding is unnecessary
There is enough food in seed and potting compost to feed seedlings. However, if you are growing in sponges or pellets/plugs, you will need to feed your seedlings with First Feed or 25% to 50% dilution of a general feed such as miracle grow.

Cause of failed germination
Sometimes a whole tray of seedlings will fail to germinate as expected. At this time of the season it is probably because of wide ranging temperatures, and in particular, it’s too cold at night.

Tomato plants grow at their best rate when temperatures don’t fluctuate too much. Keeping the temperature within a specific range (15 to 21C is good depending on available light) but this is almost impossible at this time of year for the home-grower, unless a lot of money is spent of course!

Avoiding Leggy Seedlings In Cloudy Weather

  • Give them as much light as possible – use reflective white sheeting/paper
  • Reduce watering
  • Keep temperature from becoming too high

Some varieties are prone to becoming leggy – Red Alert for example, and some will remain stocky even in cloudy weather – Tumbling Tom for example. However, most varieties will become leggy without enough light.

Two conditions seedlings hate

  • Damp air – especially when it’s cold
  • Saturated roots

Propagators with hoods
If you are using a propagator with hood, open the vents and remove the hood as soon as the seedlings germinate. This will help to reduce the threat of fungal disease and “Damping-off”. This condition is caused by fungal spores in damp conditions.

Propagator Lid

The cold weather we’ve had in the UK isn’t too bad for growing tomatoes as long as there is plenty of sunshine.

Of course, plants need to be kept indoors at night or in a heated greenhouse. However, during the day a sunny windowsill or a day trip to the greenhouse, pollytunnel or a few hours on the patio, as long as there is no wind, will do them good!