HelpfulGardener.com

Hi,
I'm growing a tomato plant in a container. Recently I noticed the dark patches and discoloration on one of the branches (see attachements). Any suggestions on what the cause of the issue might be e.g. disease, over/under watering, nutrient deficiency, etc.? I'm a noob so don't know a whole lot about growing.

Let me know if any additional information is required and I'll try to provide.

Thanks

It looks like a nutritional deficiency. How big is this plant supposed to get? Tomatoes are heavy feeders. What did you use for fertilizer?

I would repot in good soil in a larger pot . Try 10 gallon. Although most books say you can use a smaller pot, that is for a small tomato. I mix 50/50 peat moss and perlite. for 10 gallons. I mix in 1 cup of tomato or citrus fertilizer in the soil mix. Analysis 6-4-6 or 9-12-12. The numbers around 10 or less are good. The main thing is that they have slow nitrogen. Do not use organic fertilizers in small pots.

I'm growing Moneymaker which are Indeterminate. According to Google they grow up to 200cm (79") in height. Currently the top of the plant is 53cm (21") from the top of the soil.

The container is 12l (3.17 US Gallons) which may be too small, especially as you recommend 10 gallons.

I grew the plant in 100% compost (packaging says it's a reduced peat mix enriched with seaweed).

I use an inorganic liquid tomato fertilizer which has a mix of 4-5-9. I read somewhere to fertilize once every 2 weeks so have been doing that. I think I may have given 3 applications so far.

I normally water every 1-2 days, depending on the temperature.

Some people are o.k. with compost. It always causes me problems if I have more than a couple of handfuls of compost in a container. I only use vermicast for compost.

If the tomatoes are indoors, are you taking the plant outside to water it? The other thing I found out the hard way recently, was that pots with attached saucers block the drain holes. I usually take the saucers off, but I did not do that and my pots flooded because they were not draining. My plants looked better after I put more holes in the sides of the pot.

Use a potting mix in a container. Pure compost holds too much water and causes issues. It also sucks up nutrients and steals from the plants if it is not fully broken down. It sucks up nutrients after that as well and binds things like phosphorus. Aerated compost is more on the alkaline side. Alkaline conditions will make micro nutrients less available. Peat moss is an anaerobic compost. That makes it acidic. Usually, lime is added to peat moss to raise the pH to about 6.0, which is fine for most plants. At a pH of 6.0 micro nutrients are available. At a pH over 7.5 micro nutrients are less available.

To add insult to injury, mixing different fertilizers also causes problems because nutrient ratios affect each other. This is a problem I am dealing with now.

Thanks for the suggestions. I'll head to the local garden center right away and get a larger pot. And see what potting soil they have also.

What I use for tomatoes are 18 gallon muck buckets. 50/50 peat perlite and 3 cups of citrus fertilizer 6-4-6. You can also use tomato fertilizer 9-12-12. The fertilizer is blended into the mix as as starter. An indeterminate in an 18 gallon pot will still have the roots escape and go into the ground. My indeterminates get to be 8 ft tall. Container varieties and determinates are better suited to living in smaller containers. They can range from 6 inches up to 5ft. I still have determinates in 18 gallon pots, but they can probably do o.k. in a 10 gallon pot. I mix my own potting mix, so I would still have to mix the same quantity and use the rest for another container. I have never figured out the exact volume as I make the soil by the bucket. An 18 gallon container takes a little more than 2 cu ft of soil.

Although an 18 gallon container is large enough to use organic fertilizer. It requires regular supplementation. Tomato, lettuce, cabbage and beans do o.k. but the cucumbers are really fussy about the nutrients. I haven't figured it out.