How To Encourage Tomatoes To Ripen On The Plant

Great looking tomatoes but still green

If you want to know how to encourage tomatoes to ripen on the plant, then read on. It’s around the middle of September that temperatures drop and ripening outdoors becomes an issue.

However, at that time of the season, you probably have some wonderful looking trusses of tomatoes on your plants … the only thing is, the tomatoes are still green!

If the tomatoes on the lower trusses have reached their full size but are taking their time to ripen, there are a number of things we can do to help the process along.

  • Reduce nitrogen and increase potassium (potash). Too much nitrogen can delay ripening.
  • Remove all side shoots and stop the plants by pinching out the top of the main growing stem – on tall varieties.
  • Remove all flowers or very small tomatoes that won’t reach full size before the end of the season.
  • Pick tomatoes as soon as they start to turn colour.

I mentioned last week that stress can encourage tomatoes to ripen on the plant – here are a few tips on how to stress tomato plants. This is best done towards the end of August.

  • This can be done by reducing watering frequency – longer periods between watering. Of course you need to be careful not to allow plants to wilt.
  • Heavy pruning of leaf branches, if tomatoes have reached full size, will shock plants into ripening their tomatoes.
  • Cutting some of the roots by sticking a trowel into the soil about 4 or 5 inches from the stem base – a bit extreme maybe but it can work as a last resort at the end of the season!


How To Encourage Tomatoes To Ripen On The PlantProfessional growers sometimes use a “forcing solution” to speed-up the ripening process. One such solution is GHE Ripen. It gives a plant a strong signal that it is coming to the end of its life. The plant reacts by speeding the ripening process, in a last effort to reproduce.

To encourage picked tomatoes to ripen. This is a lot easier … all you need to do is to put them into a large bowl with a ripe banana or other very ripe tomatoes. The gas that is produced by ripe fruit encourages the unripe tomatoes to ripen.

Of course there is always fried green tomatoes but we would rather have the ripe ones – especially if we are going to save seeds for next season!

Blight forcast
There is not a lot we can do about blight once it gets established but taking preventative measures can help – especially if we know that blight is likely to appear in our part of the world.

Here’s a link to a website that keeps watch on the incidents of blight around the UK – just add your postcode. It is meant for those who grow potatoes but tomatoes and potatoes have blight in common!

How to recognise late blight

There are two types of blight – early and late.

Early blight is shown in the photo below, it has round concentric rings – almost like an eye shape.

Late blight (the one we call blight) usually starts by affecting leaves with patches of brown up to the edges of the leaves. This makes its way to the stem and then eventually the tomatoes.

In the photo above, the stem has turned dark in colour and the tomatoes have started to turn brown and soft.

The season so far

So far, August has been quite wet here in Devon though it should be improving this weekend. Several continuous days of wet weather in August is likely to produce late blight.

I remember in August 2008 my wife and I went to the Edinburgh Festival and it rained for about two weeks non-stop, both in Edinburgh and the West Midlands where I used to live. We arrived home to a garden full of blight – all the outside plants were affected and most of the tomatoes unedible.

Of course these days we have blight resistant varieties such as Crimson Crush, Mountain Magic and Lizzano but even they may show signs of blight on their leaves but the fungal disease should not progress further.

Here is a link for more info on how to avoid bliight:

I hope that the weather is stays fine in your area!




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Crimson Crush Seeds – be blight resistant next season!


9 Responses

  1. Diana Winfield
    | Reply

    Thanks for reply unfortunately can’t do anything about lack of sun and overwatering as all plants are outside and I can’t control weather !!
    Tried ” Supersweet Solanum lycopersicum ” tomatoes yesterday absolutely delicious . This plant has loads of tomatoes so looking forward to eating these . Growing tomatoes bit like playing lottery – great when you win !!
    Di Winfield

    • Nick
      | Reply

      That’s true … I’ve just had an email from someone who has had all his plants lost to blight!

  2. Diana Winfield
    | Reply

    Thanks for newsletter always interesting . I bought different plants and seeds this year just for a change , all looking healthy , but the two I’m already harvesting ( Patio Bush Totem & F1 Red Profusion ) are not living up to the claims on labels of being
    ” sweet” tasty tomatoes . Have I done something wrong or is it the lack of sun ?
    Di Winfield

    • Nick
      | Reply

      Hi Diana, Some varieties are disappointing even though the seed packet would have us believe they are the tastiest tomatoes ever! Three things usually affect taste – lack of sun, lack of nutrients and being overwatered. If they have received these ok, it’s probably the variety.

  3. Rhys Jaggar
    | Reply

    Funnily enough, Nick, my season sees me struggling with a few strains to still have big tomatoes left on August 22nd, which is the biodynamic day of choice to harvest tomato seeds this year! Red Alert I simply made in July, but both Maskotka and Tigerella already have my chosen toms well red and in normal circumstances ready to pick! My mega fruit on Super Marmande are already turning red and even the Black Russian favoured fruit look like being a bit early. Black Krim, Alicante and Black Cherry look like being fine….

    I guess I will sow 2 weeks later next year!

    Great ripening tips by the way. I simply stop feeding and watering in September, along with branch pruning: it may make plants lie down, but they certainly ripen up.

    Feeding with comfrey tea also accelerates things in August: fruit swell and ripen faster in my experience as a result….

    • Nick
      | Reply

      Hi Rhys, Good to know that most of your varieties are on the table or nearly there!
      Thanks for your tips about end of season ripening too.

  4. Rob
    | Reply

    Hi Nick,

    Thank you for another excellent and informative newsletter. I learn something new every week.

    This week, I read in your tomato blight newsletter (the one in your link) that you recommend removing some of the lower leaves by pulling them – and not cutting – if they show signs of infection. May I ask why you recommend pulling and not cutting?



    • Nick
      | Reply

      Hi Rob,
      The reason is because a blade may transfer disease from one plant to another.
      You could moisten a cloth with hand sanitiser and clean the blade (scissors or knife) between plants, or a bacterial wipe will do too!

      • Rob
        | Reply

        That explains why blight, once established, seems to spread through my plants like wildfire. I have always cut (rather than pulled) the affected leaves in the belief this would minimise the risk of the blight spores becoming airborne and infecting the other plants. It seems after almost sixty years of growing tomatoes, I still have much to learn! Thank you, Nick.

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