The three biggest challenges at this time of the season are to keep the seedlings and young plants in:

  • Enough light
  • Enough warmth
  • Fed (keeping up their immune system)

Enough Light
Did you know that seedlings need more hours of light than mature plants! We aren’t talking about intensity of light (blazing sun) but hours of light to stop them from becoming leggy.

A challenge for those who sow early is to stop seedlings from becoming leggy.

This can be done in two ways … reduction of water/moisture to slow growth down or artificial lighting.

Giving the minimum amount of water
This is a bit of a balancing act but OK if for short periods. Growth slows and there is a danger of plants wilting. However, if you aren’t out all day, you can keep an eye on them and mist them should they be desperate for a drink!

Turn on the light
The least expensive option in the lighting department is probably a CFL Grow Light– Compact Fluorescent Light. It looks like a big light bulb with twisted tubing.

Seedlings prefer the blue at 6400k – I use a CFL bulb a lot on my seedlings when light levels are low.
You don’t need a high wattage if you only have a few seedlings. Even a 25 watt is useful – just keep the light low over the seedlings and use a reflector – kitchen foil will do!

It’s now the beginning of May and the weather in the UK is about to drop to freezing temperatures at night.
Although many of my plants are in the polytunnel, I’ll still fleece them. This helps keep the condensation off their leaves as well as the temperature a degree or two higher under the fleece.

The best place for young plants is still inside the house, or if you can afford it, a heater in the greenhouse/polytunnel.

The idea of having the soil nutrient contents on the side of a grow bag is a distant dream – including NPK plus micro nutrient levels.

Until then, we’ll just have to guess “what lurks inside” and add the nutrients that will benefit our plants.

The problem is though, unless temperatures are reasonable, plants won’t feed anyway!
A way to give them a boost when the weather is cold, is to foliar feed at the warmest time of the day (though not in direct sunlight) in order to keep their immune system up and running.

I give my seedlings a misting with a tonic such as liquid seaweed, SP plant invigorator and there are many hydroponic boosters (including organic ones) that can help plants through the hard times.

In cold, damp and wet conditions, plants will soon be affected by fungal, bacterial and viral diseases so the challenge is to ward them off. This is difficult to do if the weather has been and remains dull, damp and cold.

To sum up
To stop them becoming leggy: under-water or use a compact florescent light.

Avoiding the cold and damp: fleece them, even in the greenhouse, and keep the condensation under control by keeping the air circulating – better still, keep them in the house where the air is less humid and less damp.

Give them a tonic: a foliar tonic/boost applied at the warmest time of the day can help keep their immune system up and your plants healthier.

Whatever you do, it’s a challenging time … let’s hope the weather improves soon!

If you have any tips that you would like to share, please mention them below.

10 Responses

  1. jess allaway
    | Reply

    Hi Nick,
    I’ve had very good results from using the 4′ warm white fluorescent tube over my seedlings. Kept them under the light until the 5″ pot stage and by that time the daylight hours were much better. Tumblers have been in final pots for a few weeks now and have pea sized fruits on them. They are looking like big healthy plants. I cover them all (inside the greenhouse) with newspaper hats overnight! So far, so good. My attempts at grafting were a complete disaster. Getting the stems to like size I found nigh on impossible. I was bemoaning the fact that I had killed six perfectly good seedlings but on doing more research online I realise that the way to go should have been to buy heritage seeds to try this out on and not expensive F1’s! Oh, well, another lesson learned! Thanks again for all your advice – look forward to the newsletters and comments from fellow gardeners.

    • Nick
      | Reply

      Hi Jess,
      You are making very good progress if your plants are already fruiting. My Red Alerts are about to start fruiting now, so you are ahead of me!
      It definitely helps to provide seedlings with extra light – it’s been difficult to stop them from becoming leggy with the low light levels we’ve had lately. They rely on good light levels to bring them into flower.
      The experts in the videos make grafting look so easy! I find that it takes longer than a week before the graft heals and usually closer to two weeks, I guess it depends on the temperatures too, but if left too long in the humid atmosphere, the small plants go down with fungal disease.
      Please keep us informed of your progress – at the moment you are our leader!

      • Nick
        | Reply

        First flower has set and fruit swelling – Red Alert again!

  2. allan
    | Reply

    thaks nick i will tyr and get one this week even if i dont need it this year i will use it next year although the way the weather is going i might need it for a while hope not though
    come on the nice weather

  3. allan
    | Reply

    looking for some advice on heating in the polly tunnel i was wanting to put a heater in it it is a 4mx2m tunnel but was wondering if anyone could recomend an electrical heater should of got one in the beginning of april but didnt
    just ordered the floiar spray thanks for the advice

    • Nick
      | Reply

      Hi Allan,
      I’ve got an electric fan heater with thermostat – the make is Parasene which I sometimes use. It isn’t big enough for the area I have so I partition off a small area with bubble wrap insulation and heat that.
      The best fan heaters/air blowers are gas powered but cost a bit to buy and to run.

  4. Bob Iles
    | Reply

    Hi Nick, I have a cold greenhouse but I bought a four tier mini greenhouse and this is inside my bigger greenhouse, I open this up every day and ventilate the main greenhouse and all my varieties are looking really good with Shirley F1 and Gardeners Delight ready for growbags. I bought some of the growbag pots that you reccomended and am looking forward to using them. Regards Bob.

    • Nick
      | Reply

      Hi Bob,
      Pleased to hear it’s going well – it’s a great feeling to put them in their final position!

  5. Rhys Jaggar
    | Reply

    Absolutely confirm the seaweed foliar spray – I’ve done that for the past 5 weeks on plants sown in the first week of March and they keep growing and look wonderfully healthy. Some plants now have 35cm ‘wing span’ as well as being >30cm tall and, as you say: too many plants and not enough window sills!

    I actually transplanted my Tumbler and Alicante into final resting places – 10 inch diameter flower pots – and gave them their first good feed of Tomorite as they are both flowering at the time of feeding. They are living inside a French Window so they can be taken outside easily when the temperature warms up again. So, if the good watering I gave them with potash food doesn’t do them good, I’ll notice in the next week or so. Hope not though!

    • Nick
      | Reply

      Hi Rhys,
      That’s a very good “wing span” – it’s great to see tomato plants at this height with good healthy leaves.
      Pleased to hear that the seaweed extract is working well!

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