Tomato Newsletter Week Six

A question that is regularly asked at this time of the season is: “when should I transplant my seedlings from the seed tray (or similar) into their own pots?”

Some growers do this at the earliest opportunity – when the seedlings are large enough to handle – at about a week or two after germination. I prefer to leave them a bit longer – until their first true leaves are about the same length as their seed leaves – three to four weeks after germination.

Seedlings in a pot
These seedlings can be gently tipped out of this pot to prevent breaking the roots. Always water after you have transplanted, or worked soil will turn into mud!

It’s good to allow the seed compost to dry out slightly so that you can prick out (or tip them out) with most or all of the roots intact.

Watering Seedlings and Establishing a Good Root System
When transplanting (potting on into a bigger pot), it is always good to encourage the roots to become established as soon as possible. This is done after the first watering – in a wet dry cycle.

Seedlings in Pots
Water from below to prevent soil compaction – also make sure that all the water in the tray has been absorbed. Tip out remaining water after about five minutes.

After a thorough watering, it is best not to water again for several days – or until you have to! This makes the roots work hard and develop well – receiving more oxygen as the soil dries out and growing in search of more moisture and nutrients.

Don’t do this …
After the first thorough watering, keep topping up with small amounts of water .This will slow root growth and prevent oxygen from entering back in between the soil particles. If roots don’t need to search for water – they won’t and their size is reduced.

Obviously, keep your eye on them as the soil dries out – if they begin to wilt, the quickest way to hydrate them is with a spray/mist of water. Then water them thoroughly again.

Weight As An Indicator
It’s good to feel the weight of pots when watered, so that you can tell when most of the water has been used up – by regularly lifting the pot.

Don’t do this either!
Standing small pots in a tray of water 24/7 will also cause reduced growth and probably root disease.

When it comes to watering, it’s impossible to keep the compost, or other media, “just moist” for very long, but by using a wet/dry cycle, we can get the best of both worlds – moisture and oxygen in the root system.

Your little plants will grow more quickly and be healthier too!

Give seedlings a day or two to recover after transplanting before putting in full sun.

A One Plant Reservoir System

I have to say that this is my favourite home made reservoir system – it’s not a new idea but has been around for some time.

  • An upturned pot sits in a large bucket.
  • The tomato pot sits on the upturned pot.
  • A capillary matting strip is used as a wick – similar to the Quadgrow Planter

This is an ideal method for all sorts of reasons … it’s cheap and one plant can fit in a small space anywhere around the garden or greenhouse.

Bucket Reservoir

The lower bucket holds plenty of water and nutrients.

You could use a bucket for the tomato plant – with holes in the bottom of course but you probably don’t need a pot that big.

In systems where water and nutrients are on supply 24/7, large containers of soil for root systems are not as crucial – the reservoir means that plants experience less stress when temperatures fluctuate widely because they always have access to water.

Issues of light and keeping the reservoir free from debris and leaves etc.

The soil surface

When watering from above, you may notice algae forming on the soil surface. This is very common in July and August as we water frequently and soil remains damp on the surface. The problem with algae is that it encourages disease and small gnats that feed off of our split tomatoes (just the odd split tomato that is!;).

A great way to avoid algae is by keeping the soil surface light proof with the use of clay pebbles.

Two or three centimetres of pebbles at the soil surface will keep the light off the soil and also encourage the surface roots into the pebbles for plenty of oxygen – a win-win situation!

Drainage – Instead of crocks

Clay pebbles can also be used at the bottom of pots.

This allows plenty of air for roots and the soil isn’t saturated at the bottom of pots for long periods. When pots are watered in trays, clay pebbles won’t cause the disease problems that saturated soil can. Thanks to John N. for the clay pebble tip!

It’s also Important to keep the reservoir light-proof

A skirt of plastic sheeting attatched to the tomato pot that overhangs the top of the reservoir bucket will stop debris from falling in the reservoir and reflect the sun from the pots on a hot day. This keeps the water algae-free and the little critters away!

Plastic sheeting – black one side, white the other – can be purchased from hydroponic stores (on Amazon too) at around £1.50 a meter. It is very handy for all sorts of jobs when light-proofing and reflecting etc.

Keep those seedlings in the light!



15 Responses

  1. Norman Mason
    | Reply

    Hi Nick
    Could I get your weekly newsletter please
    Norman Mason

    • Nick
      | Reply

      Hi Norman,
      Sorry but I don’t do the weekly Newsletters anymore.

  2. Derek R
    | Reply

    Hi Nick,
    I have over wintered some small (6 inch) Tom’ side shoot plants and I am currently transplanting their sideshoots amongst this years seedlings of a similar size (The over wintering is as a result of Commercial growers saying that side shoot plants get going quicker than seed grown plants). Seems to be working well so far.

    • Nick
      | Reply

      Hi Derek,
      Sounds good to me … It is often done in areas of the world where the winter season is not too cold. Not only does it save money, buying expensive hybrid seed, it also gets us off to a quick start. Just make sure that the side shoots are healthy and won’t pass on any fungal infections to your seedlings.

  3. Norman West
    | Reply

    Thanks Nick,I will try the Rootit F F .It has a good reputation from reading other comments left. The newsletters are a great help , lots of innovative ideas.Thanks once again.

  4. Norman West
    | Reply

    Hi Nick, my seedlings 10days old are going pale ,could you suggest a solution to get them back to dark green.

    • Nick
      | Reply

      Hi Norman, the Rootit First Feed is a great tonic for young seedlings. You may find they pick up with a bit more sun or maybe there is some other issue that is preventing them from keeping their healthy colour. Over watering, nutrient problems with the compost you are using or low temperatures can cause yellowing leaves.

  5. Jess Allaway
    | Reply

    I used your link to send away for a pot of Rootit First Feed and I think I misunderstood what I could use it for. The instructions only mention using it when sowing seeds. Do you ever use it beyond that – for young seedlings?
    Most of my tomato seeds are already germinated and awaiting planting into individual 3″ pots and I thought of giving them their first watering with FF. However at that stage I am using the usual multi-purpose compost. Would I be over-feeding by doing that? Just wanted to help in getting really good roots. Your advice would, as usual, be greatly appreciated.

    • Nick
      | Reply

      Hi Jess,
      Rootit First Feed is great for seedlings after germination – you can use it throughout the life of a tomato plant. If growing in soil, it makes a great tonic for mature plants. It is a complete feed for seedlings growing in sponges and rockwool for about six weeks after germination – after which a hydroponic feed would be required if growing without soil.
      It is fine to use during transplanting as you suggest – your seedlings will be very happy!

    • Rhys Jaggar
      | Reply


      I always use it at the 2-3 week stage, which for me is when seedlings have established in 8cm pots for 7-10 days. I have always had good response then….

  6. Keith Tucker
    | Reply

    Thanks for your information on transplanting seedlings,I normally transplant mine after a week as mine are germinated every year in a 7 tub garland heated propagator on the windowsill and they tend to go to the window for light and I have to turn the container around several times during this period I look forward to your newsletter every week thanks

    • Nick
      | Reply

      Hi Keith, I’m pleased that you look forward to the newsletter – good luck with your seedlings!

    • Rhys Jaggar
      | Reply


      I do exactly as you do and transplant 7-10 days after sowing. Whether it is optimal I do not know, but it is pragmatism given the facilities available to me. I always get reasonable crops….

  7. Anonymous
    | Reply

    Thanks Nick.
    Even at my age you can always learn something more.
    Don S

    • Nick
      | Reply

      Hi Don, you are right … there is always something new to learn – often the hard way!!!

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