Why are leaves on my tomato plant turning yellow or brown?

brown and yellow leaves on bottom of tomato plant
There are yellow and brown leaves on the bottom of this tomato plant, but that’s normal. Photo by Connie Oswald Stofko

by Connie Oswald Stofko

The leaves on the bottom of my tomato plants are turning yellow, then brown.

Don’t worry; it’s normal, says Jen Weber, vice president and manager of Mike Weber Greenhouses at 42 French Rd., West Seneca.

“That’s what happens when the plant starts making tomatoes,” she said. “It’s better to have an ugly plant with lots of tomatoes than the other way around. By the end of summer, you should have a dead-looking tomato plant.”

That’s what mine always looked like, and I thought I was doing something wrong!

If those ugly, dead leaves bother you, you can snip them off.

But if half of your plant has dead leaves at this time of year, it’s probably because you under-watered it, over-watered it, or dumped too much fertilizer on it, she said.

If you think your tomato or other plant might really have a disease, you can stop in to Mike Weber’s to ask. The best thing to do is to use your phone to take a photo of the diseased leaf or other affected part of the plant, Weber said.

If for some reason you can’t take a photo, you can snip off a leaf or other part of the plant that you believe is affected, but leave it in the car! Don’t take a possibly infected leaf or part of a plant into Mike Weber’s — you could be spreading disease onto their plants! Just tell them you want to show them what you think is a diseased plant and they will go out to your car to look at it.

Hours at Mike Weber Greenhouses are 8 a.m. to 6 p.m. Monday through Saturday and 9 a.m. to 6 p.m. Sunday.

Weber shares more on tips on vegetables below.

When to stop fertilizing tomatoes

Stop fertilizing tomato plants once they start to flower, Weber said. If you keep fertilizing, you’ll get a big plant, but no tomatoes.

tomato hornworm
Tomato hornworms can be hard to spot, but if you see one, pick it off before it noshes the plant down to the stems! Photo courtesy Eric R. Day, Virginia Polytechnic Institute and State University, Bugwood.org

Watch for tomato horn worm

Now is the time to watch for the tomato hornworm.  

“It looks like a friendly green caterpillar with a thorn on his head,” Weber said, “but it will eat your plants down to the stems!”

They’re hard to spot at first. In the photo, you can see that they blend in with the tomato leaves.

When you discover them, the best thing to do is pick them off, she said.

Tomato hornworms aren’t worms; they’re caterpillars. They bury themselves in the ground and come out as a moth.

Why is my pepper plant so small?

If your pepper plant is smaller than it should be, it’s probably because you put it outside before the night temperatures were warm enough, Weber said.

Peppers need night temperatures — not daytime, but night temperatures — of around 65 degrees Fahrenheit, she said. It didn’t get that warm until July.

“With our cold, wet spring, we lost about a month, temperature-wise,” she said. “We’ll have late vegetables this year.”

And if you’re one of the gardeners who put your peppers outside on Mother’s Day to get a jump on things, you were way too early. That’s why Weber tells gardeners to wait until the beginning or even the middle of June to put peppers outside.

“You never know” what the weather will be like, Weber said.

Eat zucchini, squash blossoms

If you’re blessed with a bumper crop of zucchini or other squash, consider eating the flowers, too.

The flowers are edible, and there are a lot of recipes online for stuffing and frying zucchini blossoms. Weber likes to bake them.

Of course, there are a zillion recipes for zucchini, too, and if you make a big batch of zucchini bread, you can freeze it for the winter.

But if you’re running out of ideas on how to use all that zucchini, try eating the blossoms instead of the fruit. It’s like getting two different foods on the same plant.

6 Comments on “Why are leaves on my tomato plant turning yellow or brown?

  1. I always worried about the yellowing of the leaves! Thank you, this set my mind to ease!

  2. Grateful for the good information. Lots of work, somewhat

    disappointed with the few veggies and plants I try to maintain,

    will remain positive.

  3. Why do my cucumbers have prickly skins. I have never seen that before. Should I peel them, is it safe to eat them?

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