Owing to the amazing weather we’ve had over the past few months in the UK, many of the problems we now experience as tomato growers are physiological, caused by high temperatures and hot sun, rather than caused by diseases.

Physiological disorders include:

  • Blossom End Rot
  • Blotchy ripening
  • Greenback – shows as green shoulders around top edge of fruit.
  • Fruit splitting – soil condition from very dry to very wet.
  • Catfacing – underside disfigured.
  • Rough and sometimes thick skin caused by wide temperature swings.

Nutrient Strength for Tomatoes

It is also the case that over and under feeding can cause some fruit disorders, so getting the nutrient strength for tomatoes right, is important.

Measuring nutrient strength

The way nutrient strength is measured is with an EC meter – EC stands for “electrical conductivity”. This measures the amount of mineral salts in water after the feed has been added.

In the photo below I’m taking the EC of my water tank that supplies my auto pots. The plants are growing in 50/50 soil/perlite medium.

Ec-Meter - measuring nutrient strength for tomatoes.

Nearly 2.3 – that’s about right for the moment!

An EC of between 2.0 to 2.5 is moderate, but the tomato grower may decide to increase or decrease the strength of the feed depending on:

  • The growth stage of plants and fruit.
  • Weather conditions – high or low temperatures.
  • The tomato variety – often, large tomato varieties do better with a stronger nutrient feed.

If the EC is kept below 2.0 or above 3.0 for a long period of time …
Fruit size may be effected, more tomatoes may suffer from physiological disorders especially blotchy ripening and blossom end rot owing to a lack of potassium and calcium respectively.

So how does this effect the average home-grower with nothing more than a bottle of tomorite and its instructions to feed his or her toms?

The EC of your tomato food

When growing tomatoes in soil (rather than other media), it is standard practice to reduce the nutrient strength to half.
Most brands of tomato food take this into account already, and when tomorite and similar type foods are diluted, they provide an EC of between 1.0 to 1.5 – that’s around half the strength you would give tomatoes growing perlite, coir or rockwool in a commercial greenhouse.

The reason why the strength of tomorite type foods is reduced is because there is plenty of food in the new soil already – at least in the beginning!

Tomatoes are hungry feeders

We know that tomato plants are hungry feeders, so by the middle of August, the soil is almost depleted of nutrients – especially if growing in containers and grow bags.

It’s at this point, with only a couple of months left of the season, that I increase the recommended strength (or double the frequency) to the level that tomatoes receive when growing in soilless media.

You are in control

Once you know the strength of your nutrients, you can make adjustments as necessary depending on growth stage and weather conditions.

A higher nutrient strength is often given in cloudy conditions and a lower strength when it is warm and bright – when plants need more water.

It’s true that feeding little and often is the best way to feed tomato plants. One reason for feeding at every watering is because whenever water only is given, nutrients are washed away from the plant’s roots leaving just fresh water – not good for growth if plants are fed just once a week!

However, too much tomorite or any other standard tomato food will eventually lead to a premature demise of the plant.

Tomato taste and nutrient strength for tomatoes

Too much nitrogen as fruit reaches maturity can produce a watery taste.
Too much potassium is considered to increase the acid level in some varieties and also reduce the magnesium uptake – a good reason to add magnesium (epsom salts) as a foliar spray.

Tomatoes and Organics

One of the issues when feeding organically is how much food to give. The problem is, organic feed can’t usually be measured by an EC meter which measure mineral salt levels.

There is a growing trend (pardon me) to use both organic and mineral feeds – the organic supplying the great soil benefits and the mineral (tomorite) feeds supplying more control over the nutrient strength for tomatoes. Organic feed, especially green teas, such as comfrey and seaweed, don’t have a negative effect if given too generously, so are ideal as a partner with mineral nutrients.

That’s about it for this week.

One of the great things about having your own weekly newsletter is that you can write about anything you like … one of the difficult things about having a weekly newsletter is that you have to think of something to say – every week!

Regards,
Nick

23 Responses

  1. ron
    | Reply

    Can you help I bought tomato fertiliser .the packet got wet and was thrown away.and i dont know how much to use.
    It looks like granulated coffee and NPK is 5 :4:10 my plants are in ring culture pots on top of grow bags ,i put the
    dry powder in the rings.How much is the safe amount

    • Nick
      | Reply

      Hi Ron,
      You should be OK with a tablespoon mixed into a gallon of water about 5 litres.
      If it should be sprinkled on the soil first, then watered in, use a teaspoonful around the stem of each plant, then water in. If you are not sure how it should be applied, the first method is better.
      Without knowing the original instructions, it’s probably best to feed weekly.
      Regards,
      Nick

  2. Norman Anderson
    | Reply

    Is it ok to eat the tomatoes if they are not quite ripe on the top, but perfectly ok otherwise

    • Nick
      | Reply

      Hi Norman, Sounds like a mild case of Greenback and some varieties always stay that way.
      They are OK to eat.

  3. Rhys Jaggar
    | Reply

    Ideas for newsletters (if you need them, of course!)

    1. Choosing tomatoes for making seeds and the best time to harvest them.
    2. Best uses for spent tomato compost.
    3. Making your own compost for next year’s tomato growing – magic additives, overall content etc etc.
    4. A survey of what feeds people have used at different growth stages this year, and how well they fared with them.
    5. A survey of yields for different strains (volume/weight/both, in greenhouse/polytunnel or outdoors) – helping people to see how well they are doing/how much more they can yet achieve.
    6. Some favourite ways to store tomatoes during the glut (sauce for cooking, ketchup equivalent, pickle, chutney etc etc).
    7. An interactive blog allowing your readers to comment on each strain they used, with recommendation/otherwise.

    Feel free to use or ignore!

    Thanks for the great newsletters again this season – always something new to learn from you.

    Rhys

    • Nick
      | Reply

      Hi Rhys,
      Thanks for the newsletter ideas … I certainly give some of them a spin later in the season!
      Cheers,
      Nick

  4. ron
    | Reply

    I have 3 plants of gardner’s delight which have lots of ripe toms ,also 2 plants of red cherry also lots of toms but no ripe ones and nearly all green backs would not recommend them. All plants are grown in ring culture and fed twice
    a week.

  5. Rob
    | Reply

    Hi Nick,

    Here’s another recipe for green tomato chutney, taken from my 1965 copy of “Adam the Gardener”. Those of us of a certain age will remember this Sunday Express weekly guide to gardening.

    4lb green tomatoes, dipped in boiling water, peeled and sliced
    1lb apples, peeled and sliced
    0.5lb onions, peeled and sliced

    Put 0.5lb Demerara sugar, 1 pint vinegar, 2 teaspoons salt, and a muslin bag containing 1oz pickling spice into a saucepan. Add the other ingredients and boil till tender.

    Regards,
    Rob

  6. Rhys Jaggar
    | Reply

    Steve

    Would you let us know where you got your Black Krim seeds from?? I supposedly bought some last year but when I grew them they were more akin to Black Russian (which are also nice and productive with it). I’d very much like to get some Black Krim for 2015 but am now a bit suspicious about veracity….

    Cheers

    Rhys

    • stephen clark
      | Reply

      hi Rhys,
      I cant remember where i bought the black krim seeds from, but ill find out for you, however i still have about 12 very large of these tomatoes on the plant awaiting to ripen, when they do ill gladly send you some of the seeds
      thanks

      steve

      • stephen clark
        | Reply

        rhys,
        i need your address to send black krim seeds to

        thanks

        steve

  7. Rob
    | Reply

    Hi Nick and fellow anoraks,

    I’m enjoying one of my best ever years for greenhouse tomatoes. This year’s plants are highly productive, with none of the greenback or blossom-end-rot problems that affected last year’s plants. This year I used Coolglass shading on the roof, which seems to have taken the intensity out of the midday sun and helped even out the daytime temperature inside the greenhouse. Coolglass is very easy to apply and even easier to remove.

    Thank you again Nick, for your wonderfully informative newsletter.

    Rob, West Midlands.

    • Nick
      | Reply

      Hi Rob,
      I used to use Coolglass, which is excellent for shading, when i grew in a greenhouse. Most of my plants are now grown in a polytunnel so I use garden fleece for shading but I think that Coolglass it more effective.
      I’m pleased you like the newsletter.
      Cheers,
      Nick

  8. stephen clark
    | Reply

    hey Nick and fellow tomato growers,
    i have learnt alot from last year when i lost over 60% of my crops to BER, this year i gone fully growing with hozelock tomato planters, after a few tweaks to modify these i have not one tomato effected by BER.
    so far, the poorest performer is outdoor girl not performing well, and the far best for yeild and quality is shirley, and in hanging basket the tiger tumbler once again came up trumps, on the beef steak size the best overall was black krim awesome fruits, enjoyed every tip you Nick have given us.

    steve clark – north shields

    • Nick
      | Reply

      Hi Steve,
      It sounds like the very early outdoor varieties that cope ok in cool conditions haven’t been able to cope so well with the hot weather. Shirley normally needs a greenhouse to do well but has done very well outside because of the amazing summer we’ve had.
      I’m pleased that you enjoyed the tips and that the hozelock reservoir system has done a good job.
      Cheers,
      Nick

  9. Derek Warren
    | Reply

    Hi Nick.
    if your readers are interested here’s a very nice Green Tomato Chukney I’ve been making for a couple of years..
    Derek

    GREEN TOMATO CHUKNEY
    Ingredients:
    • 2.5kg green tomatoes, roughly chopped
    • 0.5kg onions, finely sliced
    • 4 tsp / 30g salt
    • 1L malt vinegar
    • 0.5kg soft light brown sugar
    • 250g sultanas, roughly chopped
    • 3 tsp / 20g ground pepper

    Equipment:
    • Preserving pan or other large lidless pan
    • 7 – 10 jars with lids
    • Food wrap / cling film
    • Sticky labels

    Approximate cost: 2.5 GBP per batch (if you grew the tomatoes).
    Finely slice your onions and washed green tomatoes, cutting out any bad bits. Add to a large bowl and stir. Add the 4 teaspoons of salt, stir again and then cover with food wrap or a large plate and leave overnight.

    This will draw out lots of the tomato juices and help enhance the flavours. This step can be skipped if you don’t want to leave it overnight, just reduce the salt by half.

    I thoroughly recommend doing this step as it will reduce the time you need to cook your chutney for. Much of the cooking time is just reducing the liquid down so it’s a thick enough consistency for chutney

    Hope you all like it..
    Derek

    • Nick
      | Reply

      Hi Derek,
      Thanks for the recipe … I’ll make a recipe page and put it on there as we get closer to the end of the season.
      Cheers,
      Nick

  10. laura
    | Reply

    Hi Nick, just want to thank you for sharing your knowledge . For the first time ever I had tomatoes in July and I am looking forward to the best crop ever. I grow most of my tomatoes in the conservatory which does not get any sun from late afternoon because every August we get blight on our outdoor tomatoes and I’m hoping to prevent this. My most prolific crops so far have been Venus and Yellow Tumbling. Sweet Million and Hundreds and Thousands have yet to ripen but are looking promising. Ferline and Legend I have had a few nice fruits but so far not many flower trusses have developed . Roma and Yellow Pear have lots of trusses but have not ripened yet. Next year I think I will continue with the cherry toms but try a better mid size variety . Unfortunately in March and April my seed tray labels were mixed up so I have only been able to identify by guesswork the varieties and removing side shoots was therefore problematic. I am now having to lop the tops of the plants as they are far too tall but when I see a top flowering truss I am tempted to spare them from death but I do know it is advisable to maximise crops!Despite all this following your advice my tomatoes have been the best ever. Thank you !

    • Nick
      | Reply

      Hi Laura,
      Sounds like you are doing a great job … I often lose the label and get plants mixed up too!
      The cherry toms are the most likely to succeed and good medium varieties for vigour would are Tamina, Matina and Orkado – all are good yielders and tasty! Alicante and Ailsa Craig are also traditional medium varieties worth a try.
      Regards,
      Nick

  11. mel
    | Reply

    Hi Nick,
    With your last newsletter mentioning organic feed I use my wormery liquid but never know what dilution to use…or whether to add tomorite with it…have you any advice on this ?

    • Nick
      | Reply

      Hi Mel,
      It’s a matter of trying and seeing how the plants respond – even professional growers can take two or three seasons before they find out what strength or combination works best.
      Most organic feed contains a lot of nitrogen which is great for vegetative growth, but after the flowers start to set, you need something that contains more phosphorus and potassium “P and K” to give the fruit a boost and encourage the generative, fruiting stage.
      A good place to start would be a cup of organic liquid tea in a 10 litre watering can plus the standard tomorite type feed. Miracle grow do a very good “organic choice” feed that is high in P and K if you would rather be completely organic.
      Stem thickness is often a sign of balance … if the stem becomes too thick (thicker than your other plants) the plant is probably receiving too much nitrogen. Few flowers and fruit and a plant probably needs more P and K. Of course there’s a time delay before plants respond. It takes a bit of experience to steer a plant in the right direction, but it is a skill well worth learning.
      Regards,
      Nick

  12. John Bowtell
    | Reply

    Hi Nick,
    My outdoor tomatoes are growing even better than those in the greenhouse. I think it is because they have access to more natural nutrients. They are planted over the site of an old chicken run which I deep dug. The good summer has also helped. I think I also have over crowded greenhouses, too many plants. I will be strong willed and not plant so many next year.

    Plenty of tomatoes now as well as plums so it’s chutney time. If you would like a recipe or two let me know.

    Regards,

    John

    • Nick
      | Reply

      Hi John,
      My polytunnel is over crowded too – there’s never enough room whatever the size!
      If you have a good recipe for chutney, I’ll put it in the newsletter.
      Cheers,
      Nick

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