Tomato troubles #1: zippering, catfacing, splitting,  blossom end rot

I think that I’m safe in saying that tomatoes are nearly everyone’s favourite fruits. Unfortunately, that statement doesn’t just apply to human creatures but to a whole range of bugs and microbes.

This post will be about the physical and growth problems that your tomatoes might encounter and what to do about them. There’ll be another one about fungal and viral diseases and another about pest insects.

The most common (physical) tomato problems I’ve encountered –

Zippering

You may see a zipper pattern appearing on the skin of your tomato. This is caused by one of the flower’s anthers (the part that produces pollen) becoming stuck on the newly developing fruit after fertilization has occured.

A perfect zipper with the tab (blossom) still attached.
A perfect zipper with the tab (blossom) still attached.
Zippering can follow the growth of the fruit in a Fibonacci spiral.
Zippering can follow the growth of the fruit in a Fibonacci spiral.

I think this is the most fascinating problem that tomatoes can have. As the fruit grows, the anther gets dragged further and the line increases in length. As most plants grow much of their anatomy on a Fibionacci sequence, the result of a well formed zipper is a spiral.

Humidity is one suggested cause of zippering. High humidity makes the pollen end of the anther stickier than usual, increasing its chances of getting stuck.

Some sources have shown that the zippering occurs more frequently in cold weather, so a cold snap during flowering time could be the culprit.

Some tomato varieties are less prone to zippering but, beside growing your plants in a temperature and humidity controlled greenhouse, there’s not a lot that you can do about zippering – it will appear here and there on your tomato bushes or vines. It’s a cosmetic problem that won’t affect the taste of the fruit though it is possible that the tomato will split somewhere along the zipper and allow access to the soft insides by nefarious critters.

Cat facing

The symptom of catfacing is a dimpling and puckering of the fruit that, to some, looks like a cat’s face. Severe cases can lead to scarring and splitting of the fruit. It occurs when the blossom scar becomes enlarged as the fruit grows.

Catfacing.
Catfacing.

There are several suggested causes for cat facing:

Temperature is one factor. A spell of cold temperatures below 16 degrees for a number of days during flowering can cause it. Extreme fluctuations between day and night temperatures has been found to increase the occurence of catfacing.

It can be hard to keep temperatures constant unless you have a greenhouse. The other solution is to grow heirloom varieties that are less susceptible to catfacing.

Other possible causes are –
  • incomplete pollination
  • exposure to some pesticides
  • physical damage to the blossom
  • damage to the pistil  from insects such as thrips
  • excess nitrogen in the soil or media

Splitting

Splitting.
Splitting.

This is probably the easiest problem to resolve, though when you see it, it will be too late for the affected tomato and you’ll just have to eat it ethe way it is or compost it.

Splitting is caused by irregular watering or irregular rainfall. The plant takes on way too much water when it is over abundant and this forces the skin to split.

It doesn’t affect the taste of the tomato but the splits in the skin lay it open for attacks by microbes and insects.

To resolve it, remove the affected tomatoes and try to get your watering regime a little more regular both in amount and timing. In the hot weather, make sure that yout plants are well mulched. This helps the moisture levels in the soil stay more constant and will help reduce the chances of your fruit splitting.

It seems that splitting occurs more frequently in container grown tomatoes. It’s easy to let potting mix or soil in containers dry out and then we are all inclined to overwater the container to compensate.

Blossom end rot

Blossom end rot.
Blossom end rot.

Blossom end rot is usually caused by a nutritent defiency. The deficient nutrient is calcium and the symptom of the deficiency are discolouration, softening and rotting of the blossom end of the tomato (the blossom end is the free end,  not the one attached to the stem).

The most common cause of calcium deficiency that I’ve come across is overwatering. Lack of calcium can be caused by over- or underwatering, both of which can make it more difficult for the plant to take up this vital nutrient.

Other factors that can cause poor calcium uptake

  • incorrect pH
  • high levels of salt
  • physical damage to the plant’s roots
  • too much nitrogen heavy fertilizer

Too much nitrogen heavy fertilizer creates a lot of leaf growth and that needs calcium too for strong cell walls. Too much leaf growth can suck the calcium away from the developing fruit and cause the problem.

To treat it, remove all of the affected fruit and dispose of them as you wish. Check your watering habits and adjust them to suit. If your tomatoes are looking lush and healthy, the best first step is to reduce the amount of water that you are giving them., then see if the issue disappears. I like this technique best because it means less work!

In the hot weather, make sure that yout plants are well mulched. This helps the moisture levels in the soil stay more constant. It seems that blossom end rot occurs more frequently in container grown tomatoes. It’s easy to let potting mix or soil in containers dry out and then we are all inclined to overwater the container to compensate.

Add a calcium supplement to the plants by adding it to the soil or as a foliar spray. We have information on making your own calcium supplement at home.

One other possible factor that can cause blossom end rot is is poor fertilization of the flower..

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