Tomato leaves turning yellow suddenly

[Animal_lover]

Hello everyone,

Maybe someone else already asked this question in other threads, but I could not find the exact information. I am planting tomatoes in my tiny garden and they looked great all the time - flowered amazingly, had dark green dense leaves and produced a lot of green fruits, but then suddenly they started to look miserable. Their leaves are every day turning more yellow and shrink, while the fruits are still not ripe.

I wonder if this happens because it got hotter these days, or do they need something - more water or fertilizer (I don't want to use synthetic ones)?

Does someone have any idea what it might be?

Thank you

[Albert_136]

To me, when I see something happening 'suddenly' I first suspect too much water. That is just me and just how I react and may or may not be germane to anyone ease's problems.

[rainbowgardener]

Yes, hot weather would not by itself make the leaves turn yellow, though it could stop them from setting more fruit.

Yellowing is usually over watering or nutrient deficiency and they go together, since too much water flushes nutrients out and shuts oxygen out of the soil, making it hard for plants to take up nutrients.

Are your tomatoes in the ground or in containers?

It always helps to show us a couple pictures.

[Animal_lover]

@rainbowgardener : I will try to take some pics. Plants are in the ground. Although, I don't know much about the history of planting in this vegetable bed, as we just have just moved to this place in April and planted them at that time. They did really well - looked super bushy, but now look more and more miserable. They have looooot of fruits, though. Maybe they are exhausted and need more nutrients.

[Animal_lover]

It could be that maybe I am watering them too much with the increase of heat. Although, I water them only 1x a day. How often do you water yours?

[bri80]

Yellowing is usually over watering or nutrient deficiency and they go together, since too much water flushes nutrients out and shuts oxygen out of the soil, making it hard for plants to take up nutrients.

I agree with this.

[rainbowgardener]

It could be that maybe I am watering them too much with the increase of heat. Although, I water them only 1x a day. How often do you water yours?

Depends very much on what the weather is like (how hot, sunny etc) and also on what the soil is like (sandy, vs loamy- clayey). In very hot dry weather, tomatoes might need twice a day watering. In cool, damp weather once a day might be too much. Also "I water once a day" doesn't actually tell me very much. Are you putting a gallon of water per plant? More? Less?

Anyway while you are figuring out watering, you should probably give them some Tomato-Tone or other appropriate fertilizer.

[Gary350]

Pictures are always helpful. If CA soil is like Phoenix soil you probably need fertilizer. When I lived in AZ good fertilizer was very hard to find. When temperatures get above 90 tomatoes do much better with full shade from hot sun high noon until dark. High noon was 1:10 PM in Phoenix pole a metal rod in the soil and watch the shadow when shadow points North that is high noon. Wood ash is good fertilizer (potash) and Lime for BER. Buy fertilizer with high nitrogen but be very careful you can kill tomatoes in hot weather with nitrogen so be very stingy give the plants a tiny amount every day 1 teaspoon in a cup of water for a few weeks. If you mulched with wood or saw dust that will pull all the nitrogen from the soil. Be sure to water in the even about 30 minutes before dark. Tomatoes dehydrate really bad in full sun with no clouds all day in hot weather. I don't know what your soil is like but AZ soil is like pouring a cup of water into a baby diaper soil soaks it up and holds it, the soil surface gets dry and shades the wet soil below. 1 pint of water per day is probably enough. I had irrigation on my AZ tomatoes I soon learned I needed smaller 1 liter sprayers and reduced the spray time to 15 minutes per day in 114 degree heat. Look on the under side of the leaves for mites and bugs. Tomatoes suffer really bad in hot weather even if you keep plants alive you probably won't get any tomatoes until 75 degree weather comes again.

[Animal_lover]

Pictures are always helpful. If CA soil is like Phoenix soil you probably need fertilizer. When I lived in AZ good fertilizer was very hard to find. When temperatures get above 90 tomatoes do much better with full shade from hot sun high noon until dark. High noon was 1:10 PM in Phoenix pole a metal rod in the soil and watch the shadow when shadow points North that is high noon. Wood ash is good fertilizer (potash) and Lime for BER. Buy fertilizer with high nitrogen but be very careful you can kill tomatoes in hot weather with nitrogen so be very stingy give the plants a tiny amount every day 1 teaspoon in a cup of water for a few weeks. If you mulched with wood or saw dust that will pull all the nitrogen from the soil. Be sure to water in the even about 30 minutes before dark. Tomatoes dehydrate really bad in full sun with no clouds all day in hot weather. I don't know what your soil is like but AZ soil is like pouring a cup of water into a baby diaper soil soaks it up and holds it, the soil surface gets dry and shades the wet soil below. 1 pint of water per day is probably enough. I had irrigation on my AZ tomatoes I soon learned I needed smaller 1 liter sprayers and reduced the spray time to 15 minutes per day in 114 degree heat. Look on the under side of the leaves for mites and bugs. Tomatoes suffer really bad in hot weather even if you keep plants alive you probably won't get any tomatoes until 75 degree weather comes again.

Thank you very much for such a helpful advice! You say that tomatoes dehydrate bad in full sun, so I guess, that could be the problem. Because they started to look miserable once we got days filled with sunshine and no cloud cover. And the direct sun comes to them most of the day...