What’s wrong with my tomatoes?

garlicgirl · July 2019

I have 4 Gardener’s Delight plants growing in the greenhouse this year but they’ve developed yellow patches on their lower leaves which then turn brown. They are on an automatic watering system which was watering them twice a day, on a very slow drip for 30 mins, but I’ve reduced it to just watering in the morning. I’ve only fed them about 2 or 3 times and they now have about 5/6 trusses with the first fruits beginning to ripen. I’ve given them magnesium granules that get worked into the soil. I’ve also removed the lower leaves up to the first truss - should I take off all affected leaves? They have as much ventilation I can give them, with the roof vents opening automatically, the door is left open and the lower louvre vent left open. My dad usually has 5 plants in this space, but I thought there would be better air flow with 4.

Does anyone have any suggestions what is wrong with them? Do they need spraying with Epsom salt solution? Should the reduced watering fix it?

I have a further few plants outside in a bed which don’t seem to be showing this problem at all which makes me think it’s something to do with being in a pot?

The front of one of the leaves

The reverse side side of one of the badly affected leaves

The worst affected area. (Sorry about the quality! I couldn’t get a picture from the other side of the glass)

Johnny canoe · July 2019

I would bet that your plants are lacking nutrients like iron. I feed my potted tomatoes twice a week and I also apply a bit of lime twice a growing season to help them take up calcium. I also never had problems with my tomatoes grown in ground, when I switched to huge pots in the GH it took me a few years to solve the problems with potted tom plants.

pinut · July 2019

The small black patches are sun scorch caused by over feeding, so a form of chemical burn.

The yellowing is caused by the migration of chlorophyll further up the plant to where it is needed most.

Your plant is normal and healthy. Some people trim the affected leaves, others leave them on - it will make very little difference, if any at all.

Johnny canoe · July 2019

Oh, and you could give them some Epsom salt instead of lime.

Nollie · July 2019

That does look and sound like Magnesium deficiency. Here a summary of what the Vegetable Expert by Dr. Hessayon says:

‘Magnesium Deficiency (Yellowing between the leaf veins)

Discolouration begins on lower leaves, moves upwards...yellow areas turn brown... common and serious disorder made worse, not better, by standard feeding.
Treatment - Apply a tonic to the compost, use a foliar spray containing magnesium’

Could be the granules are too slow acting and a foliar spray would give quicker results. Perhaps try that and lay off any other type of feed?

The leaf rolling seen in the last photo is not serious and usually just a response to changes in temperature but check there aren’t any critters hiding in there.

Sounds as if you have done everything right. You will still get a crop but maybe not as good as you would have...

Pete.8 · July 2019

I don't think there's anything wrong with your plants.
Tomatoes grow quickly and the newer leaves on the upper part of the plant work more efficiently then the lower leaves, so the plant cuts the amount of nutrients to the lower leaves and sends it to the upper leaves instead and the lower leaves start to die.

Once the leaves start to look quite tatty, I cut them off completely, and also remove leaves that are touching the ground.

Be careful about using Magnesium. A bit too much can cause a lock-out of calcium which could them lead to blossom end rot on the tomatoes.

Fairygirl · July 2019

I'd also check how wet that soil is in those pots. My toms are in a greenhouse, and they don't get watered every day. Once they're in a large container like that, it can take quite a while for them to dry out. It's also not a good idea to water at night, always better in the morning, so that they're not sitting in damp soil when temps could drop.

They shouldn't be sitting in permanently wet soil, so it's a good idea to check just how wet it is further down the pot, and perhaps adjust the regularity of the watering .
I'd also agree that you can remove dying/browning/damaged lower leaves as they're no longer serving any purpose.

The vast majority of people over feed and over water tomatoes IMO.

Nollie · July 2019

I agree that tomato leaves gradually yellow and go tatty at the bottom as the plant puts it’s energy into fruit production - I usually end up with a good foot at the bottom without leaves. But I still think it’s magnesium deficiency- that particular pattern in the first few photos is quite distinctive and different to the usual yellowing I normally see...

I reread your post, and you said ‘I have only fed them 2-3 times and they now have trusses/setting fruit...etc.’. Presumably with tomato feed, which is high in potash? If so, that’s too much food too soon as the potash locks out other nutrients that the plants need, including magnesium (over watering can also wash out nutrients). I suspect, if it is magnesium deficiency, it is the overfeeding that has caused it.

I only apply tomato feed twice, once when fruit begins to set and at a midway point, but how often do others use tom food out of interest?

garlicgirl · July 2019

Thanks all. I'm glad to hear it doesn't look like anything too serious!

@Nollie I've fed using Maxicrop Organic Seaweed feritliser. Just the standard one, not their tomato one. I do have tomorite but haven't used it on them this year as I didn't want to overfeed and lock out nutrients. It seems I may have inadvertantly done that anyway!

@Fairygirl I'm sure the pots are too wet as there are Sciarid flies in the soil which I'm trying to get rid of. I went away last week and upped the watering system as it was roastingly hot, but it seems it was a bit too much! They are now down to one morning water, into a tube to take it directly to the roots. The surface is drying out but the bottom is probably still very wet.

@Johnny canoe they get watered with tap water which is medium/quite hard in my area. Do you think that will be enough in terms of calcium? Could it perhaps be too much Calcium locking out the Magnesium?

I've bought some Epsom salts that will dissolve into a foliar spray, but I'm not sure of the ratio. The packet says 35g per 4.5l, but I've seen other ratios on the internet and don't want to accidentally burn the leaves. Do any of you have a tried and tested ratio?Also, how often should I spray them?

Johnny canoe · July 2019

Hello garlicgirl,
This year I'm using dolomite lime, it contains both the calcium and magnesium. It also adjusts the ph so that the plant can better take up nutrients. I just followed the instructions when I planted the pots and I only have to do two applications a growing season. My purpose in going with lime was even though I upped the calcium the past two years, I still had some blossom end rot, so hopefully this lime will fix it once and for all.

Nollie · July 2019

I have extremely hard water, but it’s never been a problem for my toms, so I don’t think hard water is a critical issue... I wouldn’t go crazy with the epsom salts. Perhaps start with a thorough misting of the whole plant in the morning with a weak solution, maybe half what it says on the packet, since you have already added magnesium granules to the pot and see how they respond?

It seems if you intervene too much by overwatering, or feeding one nutrient to the detriment of another, that causes more problems than it solves. I must admit I never feed my veg apart from the toms and those only in a limited way. The laid back approach seems to work. I have been guilty of over-cosseting roses and perennials tho so am trying to exercise more restraint and let them get on with it!

What’s wrong with my tomatoes?

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