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Tuesday, May 3, 2016

Tomato Problems Growing in Containers

Q.I  have about 20 tomato plants, mostly in containers. They have been receiving 6-7 hours of direct sunlight every day and they were planted the first week of March. Every year, I get a handful of plants that develop what appears to be two different problems. Some develop little brown spots on the leaves, and then die. I promptly remove the affected stem but can’t keep ahead of it. I also have plants with leaves that develop yellow and brown edges. I have two plants with the spots, both are cherry tomato plants, Sweetie variety. The plant with the brown/yellow dying edges is also a cherry, Blue Berries variety.

I have 17 other plants, all close by, on the same watering schedule, with no problem.  I use drip irrigation. The plants are in high quality potting soil amended with compost and the soil gets changed and amended each season. The soil is covered with mulch.

I’ve attached some photos for you.

A.Thanks for all of the good information you included along with the pictures because it really helps me a lot to try to decipher what's going on.

We grow tomatoes in containers every year and don't have any problems. However, these containers are on the east side of a building so they gets shade from the afternoon sun.

I looked closely for disease problems and I didn't really see them but as I looked closer some of the brown spots might be the development of early blight. One of the simplest methods is to remove the older leaves at the first sign of browning. Don't leave them in the container but dispose of them somewhere else. Also remove the older leaves that are in shade as I mentioned in the other email. 

You can apply a fungicide that is labeled for early blight of tomato. Commonly these are copper fungicides. Some varieties are more prone to these disease problems than others. Next year you might try switching to different varieties that will give you similar types of tomato fruit.

One thing you didn't tell me is whether you bought these plants as transplants or if you started them from seed. If you started them from seed always sterilize the seed prior to planting. The following link tells you how to treat seed either with hot water or Clorox

The following link tells you how to treat seed either with hot water or Clorox

The scorching along the edges appears to be a water or salt problem or both. Make sure the containers are irrigated often enough so that the soil does not become too dry between irrigations. When salts are present in the soil, and this can be from soil mixes or compost as well, when the soil begins to dry than the salts begin to become concentrated and cause more damage.

I would also suggest that you either double pot these containers… One nestled inside another one with a 3 inch layer of rock or wood chips at the base… Or paint them white or shade the outside. At 95° F, the black exterior of the container will reach about 160° F on the outside and in direct sun. This can cause problems.

Water management is always going to be a challenge in containers. Water them daily if they have good drainage and make sure the soil is wet at the beginning of the day. If these containers drain extremely well, you may need a second irrigation during the day. Water management is going to help in salt management and possible scorching to the leaves.

If you use the same containers each year, make sure you sterilize the inside of the containers with a bleach solution and let them air for a couple of days before filling them with soil and planting in them. When applying the mulch to the container, keep the mulch away from the stems of the plants so that the plants do not develop crown rot.

The small brown spots on the leaves do not appear to be a disease problem. If it were a disease problem the brown spots would most likely have a small yellow halo around them. These do not. At least they don't now.

I know you are using drip irrigation but avoid watering overhead with a hose end sprayer or other type of sprinkler. Leaves that are in the shade will be weaker than those in full sun. Thin out the canopy of your tomato plants to improve air circulation around the leaves and allow better light penetration inside the canopy. You can do this by pinching off suckers coming from the crotches of the leaves. You want light penetration inside the canopy and you want air circulation. If you don't have this, disease problems are highly likely.

Feed your tomato plants with your favorite tomato fertilizer once a month after they begin to develop small fruits. This is important because plants pull nutrients from the soil and these nutrients should be replaced as plants become larger.

Take a look at this link

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