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Joined: Sun Jul 19, 2015 5:20 pm

Yellow spots on older leaves

Hi friends!! I'm growing a variety of heirlooms on my deck and a couple of them have older leaves that are developing yellow spots and curling a bit. Looks like an acute brown spot in the centres of the yellow spots are also starting to form as of today. It's been wet and hot the last few weeks, generally it's been a wet year so far. The plants were potted in organic potting soil mixed with mushroom compost and I added a handful of kelp meal in there when they were planted to their final containers. Last week I gave them all a drink of 2-2-2 fish fertilizer. Any ideas what the problem could be? Many thanks!! :)

Posts: 12911
Joined: Tue Jan 01, 2013 8:32 am
Location: Hawaii, zone 12a 587 ft elev.

Re: Yellow spots on older leaves

Hello and welcome to the forum. Please update your profile with your location and zone. It helps when answering questions when we know the conditions the plants are growing in.

Fish emulsion is a complete organic fertilizer but chlorosis on leaves are usually a sign of mineral deficiency or over watering. If you are not over watering, then you can boost the minerals by adding something like seaweed extract or azomite. If you are low in micros and the pH is not 8 then the leaf color should perk up in a very short time.

Tomatoes are heavy feeders of water and fertilizer. Any container plant must drain well. When the plants are small, they will have a lot of soil volume compared to the plant root size so you need to be careful not to overwate; especially in a plastic pot. When the plants are fully grown they need a 20 inch pot (indeterminate) as they have an extensive root system and when they are in fruit production in the peak of summer they may need to be watered more frequently, sometimes two or three times a day or you may get blossom end rot.

I don't do organic in pots, it has always caused issues for me, but other people do have good success. Some people swear by tomato tone and plant in compost. My compost has a pH of 7.8 and holds too much water so that is why I only use it to mix into my garden soil and I use an acidic fertilizer.

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