Mid Season Tomato Problems

I will add a little to this post over the next few days, but here is a starter!

We have had a fair amount of good weather lately, so most people have started picking. Others have had later crops, so are waiting hopefully to harvest some fruit.
I will try to point out a few problems that might occur with your crops from now on, as well as a few pointers as to maybe why other people's crops have been delayed.

I am mainly dealing with cordon type plants, as they are more prone to problems, as having a longer cropping period.

So let us look at those of us who have started picking or are about to.

Lets start with the problem of too much fruit, and yes it does happen. I have a slight problem in that I have too much fruit on my plant and the head is very thin and weak. I am picking the fruit off as early as I can and feeding high nitrogen as opposed to high potash, as I want to encourage more foliar growth at the moment. Planting my plants in the soil a little earlier might have eleviated this slight problem, but I am sure that once the first two trusses have been picked, then my plants will be back to normal.

De-shooting and deleafing
It is important with cordon type plants to keep de-shooting, to make sure that all the energy goes to the right places, especially with a lot of fruit on the plant.
De-leafing is also very important for good air circulation, and once the fruit is picked off a truss then the leaves have done their job, and it is better to remove them. Also, it is important to remove all damaged or diseased leaves as soon as possible to save further infection. I always tend to remove a few of the lower leaves even before I start picking, as this improves air circulation at the base of the plant, where there is more humidity, especially if they are touching the soil.

Older leaves nutrient deficencies
Some older leaves tend to lool like this, showing signs of deficiencies. I would not worry too much about it if you are feeding regularly and just remove the older leaves. The head of the plant will give you an idea if you are in real trouble and should be quite a dark green. 
If you get a yellowing of some of the upper leaves it could be Magnesium deficiency and can be cured in the short term, apply Epsom salts as a foliar feed in summer. Dilute the salts at a rate of 20g of Epsom salts per litre of water (1/3oz per pint) plus a few drops of liquid detergent. Apply two or three times at fortnightly intervals, spraying in dull weather to avoid leaf scorch.

Mildew and Botrytis

At the first sign of Mildew Botrytis or Blight I woulld recommend a preventative spray of Bordeaux mix if the weather is more humid or a blight warning has been issued in you area. Of course keep the greenhouse well ventilated if it is indoor crops, and remove and burn the affected leaves.

Is Bordeaux mix organic, you might ask.

As well as its use to control fungal infection on grape vines the mixture is also widely used to control potato blight, peach leaf curl and apple scab. It is approved for organic use and so is often used by organic gardeners where non-organic gardeners would prefer other controls.

 Botrytis  disease is favoured by cool moist conditions and little or no wind. Cool, damp, poorly ventilated greenhouses are ideal for the disease, and Botrytis blights are probably the most common diseases of greenhouse-grown crops

Blossom End Rot

Blossom end rot is not a disease, but a lack of calcium in the developing fruit. The calcium-deprived tissue breaks down, resulting in the characteristic symptoms and is more prelevent after a hot spell as we have just had.
Some people assume this means that their garden soil must be deficient in calcium. However, the real problem is that the plant is unable to absorb the calcium that is in your soil due to uneven supply of water. The condition is a physiological disorder, caused by an imbalance of potash and calcium in the compost, which most often develops if the compost is allowed to dry out while the fruits are swelling.
 It is more common, therefore, with container grown plants than with plants grown in the open garden or greenhouse borders.  However, when plants are grown in grow bags, where they have a small, shallow root run that dries out easily, it is essential to keep the soil consistently moist rather than let the soil completely dry out and then water fully. This extreme fluctuation is almost a sure fire way to induce blossom end rot.
Too much nitrogen in the soil can also cause rot. In this case, a handful of lime around the base of each plant might help. It is important to cut back on your fertilising or switch to a brand that has a low nitrogen and high phosphorous to high potassium ratio. Standard tomato feeds are usually high potassium.

So container or peat bag growers please watch your watering, especially in hot weather. Do not ever let them dry out. If you have drainage holes, it is unlikly that you will over water in mid summer. Drip irrigation is the best way to water pots and bags to avoid blossom end rot.

With outdoor plants, other conditions that may bring about blossom end rot are weather-related: extreme changes from hot to cool temperatures, stress from drought, and heavy rains after a dry spell. Try not to disturb the soil around the base of the plant.  Deep hoeing or transplanting can damage feeder roots and thereby reduce calcium uptake.

Splitting Fruit
Tomato fruits can suffer from splitting and cracking in late summer. This is difficult to prevent, as it is caused by fluctuating temperatures and water supply, which can be the downside by overwatering your plants to avoid blossem end rot. But as least you can still eat the tomatoes!

So here are a few tips to help prevent it. Feed regularly to maintain high soil fertility. Special tomato fertilisers have high levels of potassium to encourage good fruit development. Water to maintain a constant level of soil moisture. This is especially important when growing in growing bags, pots or other containers. Outdoors, water to maintain as constant a level of soil moisture as possible. Plants grown in border soil, indoors or out, usually have a more extensive root system which helps protect them from fluctuations in water supply. 

The dreaded blight and tomato leaf spot
 I did get some blight last year, but managed to contain it by spraying with a Bordeaux mix. make sure you remove and burn all the effected leaves first, and wash your hands and equipment throughly.
The blight spread from my potaotes planted too close to the polytunnel.
You can use Bordeaux mix as a preventative spray, and some people advise using milk, diluted 50%.

There is more about these diseases in another section on my blog, but I will just give a few warnings and pointers here. The first thing is that there are two types of blight; Early blight One or two spots per leaf, approximately ¼ to ½ inch in diameter. Spots have tan centers with concentric rings in them and yellow halos around the edges.

Late blight.  Spots start out pale green, usually near the edges of tips of foliage, and turn brown to purplish-black. In humid conditions, a fuzzy mold appears on the undersides of leaves.
There is a lot of infomation on the net about blight and tomato leaf spot, but this link will help you if you are trying to spot which one you have.

Tomato leaf spot
Numerous brown spots appear on the leaves, approximately 1/16 to 1/8 inch in diameter. The spots lack a yellow halo and, upon close inspection, have black specks in the centre.

White fly, red spider, caterpillar and leaf minor, are also problems that you might get, all of which are covered in my 'pest and disease' section.

OK what about people with little or no fruit or delayed crops.

Again, here I will mainly deal with cordon type plants, as determinate plants tend to look after themselves if you leave the shoots on and maybe just remove a few lower leaves on some varieties to give a bit of air circulation and fend off disease. But as I have said, they tend to be shorter crops, so get usually less problems.

SHOOTS, Shoots and Shoots. Time and time again I see pictures of people's plants, overloaded with shoots and suckers, which is why I have posted quite a lot about it. They just do not realise that the main reason their plants have weak and feeble trusses with poorly developed and unset fruit is mainly because they have simply left too many shoots on. Some advice that I have read is that more shoots mean more leaves. However, cordon plants have developed to have enough leaves for the fruit that they will produce. 
I have grown thousands of tomato plants, please trust me on this one.

OK, so what if it's too late and you have too many shoots and you want to rescue your plant, as I am sure you do not always want to be told what you have done wrong, but what can you do about it?
It really all depends on the state of you plant and how bad it is, but first of all remove all the suckers. These grow from the base of the plant and tend to be harder that shoots, they are usually easy to snap off, no matter how long they are.
If your plant is really overgrown, you can cut a few lower shoots off after a truss and a few leaves. This might actually help control the plant, because a plant with no setting fruit tends to just keep growing without producing any fruit, it just gets tall and leggy, and you will run out of space.

The other thing that will help is a high potash tomato feed, (tomato feed) potash works on fruit developement and if you feed a normal plant feed with high nitrogen, then you will just make matters worse by encouraging more foliar growth.

Leggy Plants
This problem started way back, with poor light levels. Not a lot you could have done about that, but a polytunnel or greenhouse will have greater light levels that a window cill in the house, so unless it's really cold, get your plants into higher light conditions as soon as you can next season.
You need to control a leggy plant by getting fruit on it, so a little early feeding when you have a few trusses will help.

Poor Setting
There are a few reasons for poor setting, the first is too low light levels and temperatures when the plant was developing. You cannot do much about this, unless to spend money on heating a greenhouse, but I do not think it is worth it for a few plants. Just make sure you sow at the right time. Too early and you will probably have worse plants that ones that you sowed later.
Poor setting can also be caused by not enough humidity in very hot weather, I tend to spray my plants with a hose a few times a day in really hot weather. I also use the water jet to shake the trusses, which helps distribute the pollen, if it is ready to burst out of the pollen sack inside the flower.
In damp weather, just shake the wire that plant is tied to, or shake the trusses gently.
Please do not worry about sunscorch on older plants when spraying them in hot weather. I have been spraying mine daily with temperatures over 30 degrees with no scorch at all.


  1. What about some yellowing of the leaves? am I lacking some nutrient? magnesium perhaps?

  2. It could well be Matron, but hard to say without seeing the plants. Post some pics on your blog.
    Older leaves do go yellow, and lots of things do affect nutrient take up by the plant.

  3. Or just email some pics, email is on my profile.

  4. Hi
    First year growing tomatoes. I have had some problems. The tops of the plants didn't grow or branch out and the leaves/ flowers went 'thick' like young curled ferns. Rest of plant was green and healthy.
    All my tomato fruits have grown at the base of the plant and I am struggling now with blight despite spraying with bordeaux mixture.
    The tomatoes have now gone from the dark green to a very light green, how long normally before they turn red, as I think I am now racing against the clock?
    Are any varieties of tomato blight resistant?
    Thank you

  5. Hi Anonymous
    What variety did you grow?, as that sometimes makes a difference to growing habits. Have you also been feeding the plants,are they outdoor or indoors?
    Some varities are less susceptible to blight,but tend not to be the best tasing or cropping.
    Bordeaux mix will help stop blight spreading, but nothing will kill it. You have to take off and burn all the effected leaves.
    Spacing plants wider and trimming off lower leaves will help air circulation. Also not growing potates too close to tomatoes helps, as it usually spreads from potatoes.
    To help your tomatoes ripen, you should stop the head of the plant, quite a few people seem to have had slow ripening fruit this year. It would be better if I could see a picture of your plants. You could email me some, my email is on my profile.

  6. Steve, this is the second year I've grown toms - outside and under plastic roof. Both years, the bottom parts of the plants have produced really well. But the upper half have had hardly any toms grow or even set fruit. Last year we had a very hot spell and I thought it was the heat as some of the flowers stems fell off. But this year is milder, the stems fall has not happened. But again, not much fruit about 1/2 way. Any ideas? Many thanks... great site! L.

  7. Hi LJ
    Just got back from a few days away, will reply in the morning.

  8. Hi LJ.
    Once a plant is loaded with fruit lower down, it really needs constant feeding to keep producing, which could be your problem. Commercial growers feed at every watering to produce a long season crop. I did have thin plants and some poor setting on mine when they were full of fruit on the lower trusses. So I had to feed every other day. It also depends on what you are growing in as in the soil they have some reserve of nutrients. Very high heat can cause poor setting if the humidity is low, which is why I spray mine with water a few times a day when it is really hot.
    It is also important to take the shoots off often, and to de-leaf to get some fruit off as early as possible.
    How do you grow yours and what was the treatment you gave them.


  9. Hi Steve, sorry for delay, been away.
    Early spring I prep'd the beds with compost, steer manure and seaweed - well dug in and left for 1 month. Covered it with black tarp for 2 weeks. They are watered with drip system nightly (45 mins). I have feed them once each with compost & nettle teas, and twice with fish fertilizer...
    I deleaf once when tall enough - removing all very bottom leaves to avoid getting wet and once more to thin out the leaves and to encourage going red. The first is earlier on, the second I did just two weeks ago.
    BTW, thx so much for the advice! L.

  10. Hi LJ, it sounds as though they have had good treatment, although maybe too much nitrogen from the nettle tea, comfrey has more potash or a commercial tomato feed can be used about once a week. The plants are under a lot of strain when fully ladened and potash does help with this. Although you did say it was not so hot this year, in poly tunnels heat can be a problem.
    I must admit my plants have been quite thin this year and a little poor setting higher up.
    next year I think you should feed more often, when the plants are full of fruit.
    I tend to leaf every few weeks as the fruit ripens, to help clear the fruit slightly quicker.

  11. Steve... and I have several comfrey planted this year. So I'll give them some tea each week next year and let you know what happens. Many thanks for your help. L.


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