[oldgrunge]

Some of my tomato plants, mainly the cherries, Sungold and Black Cherry, have developed purple tinged leaves, which eventually wither and die. This happened last year too, the fruit seems unaffected. They are growing in MP compost, in buckets in the greenhouse.
Any ideas, please?

[Annen]

My tomatoes that are/were outside did that this year and I have put it down to all the rainwater.  I kept forgetting to empty the tray the pots were stood in so they were standing in water quite a lot. The one at the high end isn't so badly affected.
But another variable is that the two which died were San Marzano and the one which has survived (just) is Gardeners Delight.
Take your pick on causes.

[Headgardener22]

Purple leaves tend to indicate cold (unlikely at the moment) or lack of nitrogen. Are you still feeding them?

[mumofstig]

Potassium deficiency turns leaves purple according to the RHS
https://www.rhs.org.uk/advice/profile?PID=456

Potassium deficiency
•Symptoms: Yellow or purple leaf-tints with browning at the leaf edge and poor flowering or fruiting.
•Cause: Potassium is needed for controlling both water uptake and the process allowing plants to harness energy from the sun (photosynthesis). Potassium promotes flowering, fruiting and general hardiness. Shortages are more likely on light, sandy or chalky soils where potassium is easily washed away. Clay soils, by contrast, hold potassium within their structure.
•Remedy: Apply high potassium fertilisers such as sulphate of potash, tomato feed or certain organic potassium sources derived from sugar beet processing.

[Debz]

I am siding with Headgardener on this one.  I think its cold too but then I think my plants are actually turning blue with the cold.  The weather here has been dreadful this summer.  We've only had a couple of days that were over 20 and most nights are lower than 10. 

[mumofstig]

Has Wales actually been that cold? I didn't think it had 

[Aunt Sally]

We've had some very cold nights down in the SE of England recently.  1^oC one night

[mumofstig]

If we did get that low, none of my plants noticed it  and the greenhouse doors have been wide open for months.......

[oldgrunge]

Has Wales actually been that cold? I didn't think it had 

No Mum, North Wales has been pretty average, daytime temps. In the high teens, mainly, with nights in the greenhouse around low teens. Although we had one night recently down to 7deg. In there.
You have given me food for thought, literally! With your comment re potash. I feed twice a week with Chempak tomato feed. But maybe they are still not getting enough. May try a feed or two of potash and see what happens.
Will keep you posted.

[JayG]

Do you mean the leaf edges are tinged purple, or are there purple blotches all over them?

Tomato leaves are notorious for frightening their owners with a variety of spots and colour changes when things aren't perfect for them - I've just had a look at my outdoor (open cold frame) and indoor (GH) toms, and some have purple spots, which start mostly on top, but sometimes underneath instead - when you can see it both sides the leaf has more or less had it.

All the leaves affected are nearest to the glass in the GH, or near the top of the cold frame, which makes me suspect it's probably due to cold - I'll just take them off when they get really manky (technical term!)

A link HERE to pictures of various deficiency symptoms (towards the bottom) - if you're not paranoid about your tomatoes now you probably will be after reading it! 

[sunshineband]

Those are excellent photos JayG, and really helpful. Thank you 



I am resisting rushing down to the greenhouse to check all the leaves now 

[oldgrunge]

Agreed. Excellent pictures, I think my tomatoes have got all the problems! Seriously, looking at the pics, think Mos is right, and it could be potassium deficiency.

[sunshineband]

Agreed. Excellent pictures, I think my tomatoes have got all the problems! Seriously, looking at the pics, think Mos is right, and it could be potassium deficiency.

Tomato food at the ready it is, then 

[oldgrunge]

Today, I gave the worst affected plants a feed of potash. Will see if this has any effect.

[mumofstig]

The purple leaves won't go back to green, but no more should grow - if that was the problem.