Feeding Tomatoes Every Watering

It’s always good to arrive home from holiday to find that the watering system did work – phew…that’s a relief! Some plants may be over or under watered but if they are still alive – that’s a bonus!

Feeding Tomatoes At Every Watering

It’s amazing how much growth can be made in just one week but we don’t notice it so much when we see our plants everyday.

As you probably know, I use different growing systems including the Auto Pot easy2grow and the Quadgrow Planter to name but two and they both feed tomatoes every watering. The plants in these systems are always watered well when I’m away.

The plants are showing…

  • No sign of stress in their leaves – curled leaves are often a sign of plant stress.
  • No split skins in the Sungold variety – this variety often splits its skins.
  • Only one tomato with blossom end rot (out of about 400).
  • Good long trusses of consistent size fruit.

The photo in the right sidebar is a Piccolo variety growing in a Quadgrow planter. Notice that the leaves are stress-free and healthy looking.

When a tomato plant has access to water and nutrients 24/7, potential problems are reduced greatly.

This season I shall remove more leaf branches owing to the good weather and vigorous growth of the plants. On a plant with around seven trusses, I’ll gradually remove leaves up to the fifth truss.

It is best to remove the very small tomatoes at the end of the bottom left truss to encourage growth in the rest of the truss.

Sometimes trusses grow another leaf and side shoot at their tip. Also leaves can sprout a side shoot from the middle of their stem!

These are signs of increased vigour owing to the bright warm weather and could also be the result of too much nitrogen or a high nutrient strength generally.

In contrast, here’s a photo (below) of a Roma variety growing in a large pot. It has suffered from stress caused by under/over watering in hot weather. The leaves don’t know which way to turn and the fruit are also of variable size with tough skins.

In moderate temperatures, water is available on a more consistent basis and tomatoes grow to a more consistent size.

Roma stressed leaves and fruit
Roma – stressed from inconsistent watering.

Nutrient Strength – Measured in EC – Electrical Conductivity
A few seasons ago, I tested the strength of several well known brands of tomato food.

Here are the results of my EC tests – if your brand isn’t in the list below, Doff and Maxicrop for example, it should be around the same EC as Tomorite and Grow Sure.

The tests were carried out with the recommended dose of each brand. For example, 20 ml in 4.5 litres of water, then the water was tested to find the nutrient strength.

The background EC strength of my tap water is 0.16

  • Tomorite EC 1.9 – also contains seaweed extract.
  • Gro Sure (Westland) EC 2.0 – contains seaweed, magnesium and iron.
  • Verve (B&Q) EC 1.9 – with seaweed extract, magnesium and wetting agent.
  • Grow Your Own (Homebase) EC 1.2 – a basic feed that is weaker than most other synthetic nutrients.

When growing in soil it is usual practice to feed nutrients at 50% of the strength that would normally be given to hydroponically grown tomatoes.

This means that if hydroponic tomatoes are given an EC of 2.0, then an EC of 1.0 is perfectly good for plants grown in soil – in containers, pots and grow bags.

The EC of the following brands: Tomorite, Gro Sure and Verve are all around 1.9 to 2.0.

This means that if you feed your plants half strength at every watering, it will be an EC of around 1.0.

When growing hybrids and large varieties, I would increase the EC to around 1.5 for growing in soil. This would be around 75% strength at every watering.

Alternating between half and three quarter strength is another option.

Measuring amounts for feeding tomatoes every watering.
If for example, 40ml is the standard recommended measure for 10 litres of water.

Half strength (50%) is 20ml in 10 litres of water.

75% strength is 30ml in 10 litres of water.

  • Miracle Grow Fruit & Veg (organic) EC 3.0 – (that’s higher than most other feeds) this feed looks great, dark and full of nourishment, but the term organic may be slightly misleading. It is a feed that is created by organic methods but still contains chemicals.

I would give this at 33% strength to my tomatoes growing in soil – pots and grow bags.

A true organic feed would register very little on the EC scale. For example, Bio Bizz Bloom is 0.6 and Doff Seaweed Extract is 0.2 … my tap water is 0.16!

A quick word about organics.
Plants don’t absorb true organic feed immediately – it has to be processed by soil microbes into a state that roots can absorb.

This means that if you are feeding plants organic food, Including seaweed extract, as added to the synthetic brands like Tomorite, you need to encourage friendly bacteria and fungi to develop in your soil.

Tap Water
Tap water contains chlorine (and other stuff) which kills friendly soil bacteria. However, if you fill your watering can and leave it overnight, much of the chlorine vanishes and isn’t so harmful to your soil microbes – friendly bacteria and fungi. This will help the soil microbes and your plants will be fed more quickly.

Seaweed, for example, contains plenty of potassium and important micro nutrients, is then able to be processed by soil microbes, and absorbed by the plant’s roots.

General Feeding Points to Consider – Feeding Tomatoes Every Watering

  • Over feeding usually produces a lower yield and smaller fruit.
  • If feeding at every watering, reduce to half the recommended strength.
  • However, a higher strength feed is considered to increase the taste and nutritional value of tomatoes.
  • It’s best not to increase the nitrogen levels as we come towards the end of the season because it can reduce the taste and slow ripening.
  • Hybrid F1’s usually prefer a slightly higher strength because of their vigour – reduce the strength if they become too leafy.
  • Large varieties often prefer a slightly higher strength because they have more growing to do and have greater nutrient requirements.
  • Standard, open pollinated varieties are often content with a slightly lower nutrient strength – their growth rate is often slower.
  • It is important to have plants in a grow bag that prefer the same nutrient strength. This could be three hybrids, three open pollinated standards or perhaps three large beefsteak varieties.
  • John Innes (clay based soil) is much better at retaining nutrients and moisture than green composted soil. It’s therefore more important to feed at every watering, or more often, when growing in ordinary multipurpose compost than in John Innes.

Adjustments for weather
If the weather is very hot, it’s important to reduce the EC because the higher the nutrient strength, the slower that a plant can absorb water through its roots owing to osmosis.

In other words, pure water is more quickly absorbed by roots than water with nutrients in it. So, if healthy plants wilt in hot weather, it may be that they are unable to absorb water fast enough owing to there being a high strength of feed in the soil.

In cloudy weather when light levels are low, and transpiration (moisture loss) is slow too, nutrient strength can be increased because plants are absorbing less water.

Divergence of Opinion
There is no one ideal method or one ideal strength for all varieties, when it comes to feeding tomatoes. Many tomato growers have their own methods and preferred nutrient strengths and also have their own formula for the various stages of a plant’s growth.

In the end it comes down to experience and finding out what works best for the varieties that you grow in your garden and greenhouse.

In Conclusion
The most successful systems for growing tomatoes for the hobby grower, that I know of, are the Quadgrow Planter and Auto Pot System.

Both methods feed and water tomatoes 24/7. This means that plants can decide how much water and food they need – as they need it – rather than have an abundance one day and running low the next.

If I could sum it all up in one word, the word would be “stress”.

Water stress, nutrient stress – too much or too little of either will stress a tomato plant. Of course we can use a little stress to force tomatoes to ripen more quickly. However, for general growth, a stress-free tomato plant is a happy plant that produces a lot of high quality tomatoes!

I hope I have given you some food for thought!



Quadrow Planter – Get 10% Off by entering WGNEW at checkout!

Crimson Crush Seeds – be blight resistant next season!

11 Responses

  1. AJ
    | Reply

    What is the Variety of the tomatoes above. Mainly green Incredible abundance?

    • Nick
      | Reply

      I think there are Piccolo.

  2. Tomato grower
    | Reply

    Thanks and great info!

  3. Tomato grower
    | Reply

    Thanks for the info

  4. Rick
    | Reply

    I have Quadgrow system and grow tomatoes and cucumbers … and due to nature of the system, feed every ‘top up’
    You mention Quadgrow … did you test their 2 part feed?
    I have followed manufacturers advice of 6ml of each A and B per Litre.
    Just mixed up my last 2 packets …
    so thinking if sticking with their packets is best or looking at alternatives.

  5. Rhys Jaggar
    | Reply

    My Quadgrow currently houses some of the best tomatoes I have ever grown for competition, four or five trusses of Zenith. I started feeding them 20ml Tomorite in 2 gallons of water three weeks ago and the fruits are swelling beautifully without starting to ripen, which is just what I want for about three more weeks.

    This year, this may be due to the heat in late June and early July being at the time when rapid vegetatitve growth and fruit set was occurring, whereas the past two weeks have been more uniform 19-24C max, 13-15 min, ideal for fruit swelling.

    My March sowings experienced the heat when much fruit set had occurred and the crops are early but slightly less bountiful in some cases. First harvests came 17-20 weeks after sowing. Tigerella may be finished by the middle of August.

    I must say I have found my Quadgrow purchase to have been a great success, acting on your recommendation three years ago. To date, Zenith, Tigerella and Sungold have all grown beautifully in it.

    Next season I may need new capillary matting: do you have any good recommendations of where to buy it, Nick?

    • Nick
      | Reply

      Hi Rhys, If you only want a small amount for the Quadgrow, Wilco’s is an option. For larger amounts ebay is the best value.
      Good to know the Quadgrow purchase has been a great success!

  6. Jess Allaway
    | Reply

    Hi Nick,
    Your “food for thought” or thoughts about food have made me decide to try one (or maybe two for comparison) of the systems next year. It has been a trying season so far here, going from much too hot when at the seedlings stage to long spells of constant drizzle and rain these past weeks. Have been removing lots of foliage but always leaving one leaf between trusses. Should the fruit be well developed – just needing ripening – before removing all leaves up to say four trusses, or would you do it even if the lower trusses were still growing in size? Hope you are having a good season.
    Best regards.

    • Nick
      | Reply

      Hi Jess, I normally leave the leaf branches on until the first few toms on a truss have started to turn colour, or most of the truss has reached full size.
      It’s not so critical for cherry toms but for the larger varieties I usually prune the trusses so that the smaller toms at the end of a truss are removed.
      The amount of toms to keep depends on their size and how much time there is before the end of the season – the more you prune, the quicker the ones you keep will ripen.
      Having a great season thanks!

  7. Chris
    | Reply

    Thanks Nick

    • Nick
      | Reply

      You are welcome!

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