TomatoPlants - Purple/Dark/Sooty Stems

[Baz]

Hi all,

First post, so no doubt I'll get something wrong

I have grown tomatoes from seeds this year, and have 18 plants. A mix of:

Tomato 'Mountain Magic' F1, Tomato 'Shirley' F1, Tomato 'Sweet Million' F1

They were super healthy (and still are), have just started flowering and the first green tomatoes are appearing and I've noticed nearly all of them are starting to get a dark stem, starting at the bottom, but also in some cases where any branches spread out. The colour is between a soot colour,grey/black and purple. The leaves are all healthy,no spots, no fungus, and all plants are flowering and are otherwise very healthy.

I'm not sure if its a sign of lack of nutrition(I feed tomorite at alternate feedings), too much water (I water every 3 days) or a blight. A blight would be strange as its all fresh soil, from seed, and grown in 4 different locations around the garden (albeit they all started by seed in the greenhouse).Or because I went on holiday and came back and they had massive suckers on, so I removed probably a third of each plant that wasn't needed.

I'm from North England so it's only about 10 degrees at night lately, too cold?

Really at a loss, is it benign or the death of all tomatoes?

This is a vid of 1 plant, as you can see I only learned to focus half way through:

https://youtu.be/aFz2yPrJTPA

If anyone can advise would be really appreciated

Thanks

[imafan26]

Some of that purple I think is nutritional. I don't really see sooty mold and the leaves did not have sooty mold from what I could see. Check under the leaves for white flies, aphids or scale. They are the usual causes of sooty mold and the mold would be on the leaves as well as the stem.

Your pot is too small. You should probably be in a minimum 5 gallon pot for a determinate or small tomato but I prefer 18 gallon pots for larger tomatoes. Tomatoes are heavy feeders and of food and water and have a large root system. A mature tomato can drink up to 4 gallons of water a day. Pots should have potting soil not garden soil. Garden soil is heavier and does not drain as freely as potting mix. It also contracts more when it dries causing water to go around the root ball instead of through it.

[Baz]

Hi,

Thanks for the reply, excellent information thank you.

There are no aphids/white fly/scale (I check at least once a week), no mould on any of the stems or leaves. The leaves underneath and on top look perfect to me, green no blotches or problems, from what I can see. Literally just the stems turning dark/purple. I'll upload a better picture of one of the plants in the next hour or so

The soil I used for all of the plants was this:
https://www.homebase.co.uk/en/homebaseuk ... 50l-204607

A few people have mentioned my pots are too small, I'll grab some big ones at the weekend and pot these on! I need 18 and they are around £5 each so I hope they last a few seasons

[Baz]

Hi, so here's another vid of a different tom. plant (I braved the weather). Very purple stem, and purple in between the joints of branches. But the leaves (tops and undersides) and (1) fruit are very healthy:

https://youtu.be/vqCKiuN-ELo

I'm curious if because my pots are too small (the roots were coming out the bottom 2 weeks ago) this could maybe be a lack of pottasium? So perhaps solvable by upping the pot size, adding new soil, and letting it fix itself after? Out of 18 plants, 13 have different degrees of purple running through the stems and branches.

[applestar]

I'm from North England so it's only about 10 degrees at night lately, too cold?

I think "too cold" is something to consider if it's possible that the temperature had gone down just 2 more degrees °C to 8 or 9. Is the lowest overnight temp of 10°C based on your own thermometer or local weather report? Your garden might be in a colder local micro-climate like bottom of a hill, shaded in the afternoon to sunset hours, etc.

[Baz]

Local weather report. Tomorrow will be 9°C at night, so definitely likely it's hit 8°C over the last week.

Half of the plants are outdoor, and half in the greenhouse. I'd be surprised if the greenhouse got under 10°C however, albeit the purple is less pronounced on the greenhouse plants.

[Baz]

I have re-potted them into much larger pots with extra soil, fed them 'ChemPak Trace Elements' (minerals: Cu, B,Fe, Mg,Mn) and I live in hope. I've trawled the internet and can't seem to find anything close to a definitive answer as to the purple colouring, which is strange as I've seen it in mine for 2 years running, my Dads, and 2 garden centres, and the tomatoes are never affected. Logic would say a deficiency of some sort, and not a blight. Perhaps it's a North England climate thing, and that's why I can't find information anywhere! Will confirm if big pot + more soil + mineral trace elements works.

[Toxic1979]

I'm about the same latitude as Liverpool, somewhere near 52/53. I would imagine anywhere near Edinburgh is at least 55/56. We probably get very similar climates, as I usually see low temps in the evenings (anywhere between 8-15 celsius, 15 being rare), and higher temps in the day (upwards of mid 20's).

I grow my tomatoes in raised beds, but Ive installed hoop houses over them and covered them in plastic to help maintain higher temps in the evenings, and to facilitate some control over the rain we get. Sometimes it can rain for upwards of 5 days straight with 10mm per day. Helps keep the soil from splashing onto the plants as well. The pain in the neck is having to uncover the hoop houses each day that the weather gets warmer. I have two full beds (18 plants of dif varieties) that are doing well outside using this method.... so far! Its also my first trying this method. So far lots of green tomatoes, that keep getting bigger. It was also very cheap to install.

[PaulF]

What I see are several branches snipped off and what is left are a lot of stems and not enough leaves. Tomatoes need a lot of leafy green to keep the plant healthy. A larger pot and remember to replace nutrients every ten days or so by adding liquid plant food. Watering will flush out nutrients in containers no matter the size. At this stage of growth tomatoes need fertilizer lower in nitrogen and higher in P and K. Purple in seedlings is a magnesium deficiency caused by lower temperatures which is corrected early on with increased temps.