How often should you water your tomatoes? Here are 5 tomato growing care tips

Picture of Paul Cappiello Ph.D.

Paul Cappiello Ph.D.

Yew Dell Botanical Gardens Executive Director

Along with “how do I prune my hydrangea” the “what’s wrong with my tomato” inquiry has got to occupy the top spot in the Universal Garden Question Hall of Fame. Indeed, a quick online search of tomato-growing challenges will return a list of something like three hundred quadrillion internet sites that will  make you want to throw in the towel, give up gardening and take up competitive checkers or join the International Corn Hole Federation instead of gardening.

But the truth of the matter is that while there are lists upon lists of insects, diseases and other disorders that can make tomato growing a challenge, there’s a suitable solution to deal with most of those problems. The $64 tomato is still alive and well as a gardening pursuit.

The top 5 things wrong with your tomato

1- Water

This might be a surprise for some people but water – too much or too little – can do more to reduce yield or quality than just about anything else. It’s just that the problems that arise from water challenges aren’t always easy to directly connect to a reduction in bounty.

While I’m sure you’re all like me and do a perfect job of irrigating your tomato plants… through every hot, dry day… week… after week… after hot, mosquito-swarm-filled week, there are some folks out there who don’t always time it just right.  And while it’s easy to see when plants start to wilt from lack of water, drought-induced plant productivity starts to suffer long before visible wilting sets in. And when drought stress does develop in a young tomato plant it can take days before the internal tomato works return to normal no matter how much you water or sing to your plants. One missed watering a week, repeated week after week can mean your plants actually never achieve peak performance even though plants may look happy and normal. 

On the other hand occasional over watering can be just as problematic, especially when combined with a spate of under watering. You go away for a week or two of vacation. You hire the neighbor kid to come over every day to water your prized tomato plants. He comes over once for the entire week. You get home from vacation, feel sorry for the half grown fruits on your slightly wilting plants. You make up for your absence by drowning the plants in an Olympic swimming pool’s worth of guilt-induced irrigation. And a few days later you have a crop of tomatoes with split skin from the rapid size increase.

There’s no substitute for consistent watering.

2- Tomato Horn Worms

While it seems entirely inconceivable that 4-inch-long caterpillar with a railroad-spike-sized horn at the end could possibly hide on any plant, that’s exactly what tomato horn worms do. These monsters of the caterpillar world so perfectly blend in with their surroundings that sometimes the first sign of them is when you go out to water one day and realize you have a nothing but a great big pile of leafless tomato stems. Add to this that adult horn worms can lay eggs every night and in perfect conditions can lay as many as 2000 eggs in a season and I think you get the picture. 

You can pick them off the plants and drop them in a bucket of soapy water if you don’t mind the wrestling match (they don’t sting with the big “horn” by the way.) You can also treat them with a natural enemy of the caterpillars – Bacillus thuringiensis (BT for short) a naturally occurring bacterial disease that is quite effective. And if you see what look like little white grains of rice on your horn worms, leave them be. They are most often cocoons of a parasitic wasp that are very effective at killing off horn worms.

3- Yellow, Diseased Leaves

By my count there are something like 64 bazillion viral disease organisms that can attack tomato plants. They all generally result in some kind of yellowing of leaves. First bit of advice is to not even bother trying to figure out which of those 64 bazillion is to blame. There’s not much to be done about it anyway. The most effective thing you can do is plant disease resistant varieties. 

And this is a good point to clear up one big issue with tomato plant cultivation. If you are growing modern hybrids, you’re in good shape. You have plants that have bred into them some excellent disease resistance. As long as you don’t grow tomatoes in the same spot year after year, you should get a reasonably long productive season out of them. 

If on the other hand you are growing the so called heirloom varieties, you’re on your own. Some of the older varieties are among the most flavorful on the planet and I can’t imagine a summer without a Mr. Stripey, Ox Heart, or Japanese Black Pear. But for all they offer in flavor and aroma they are miserable to grow. They’re susceptible to just about every foliage disease on the planet and generally struggle to make it through the end of the season. But is that a reason not to grow them? Not at all. Just be realistic about expectations and don’t waste time trying to control the foliar diseases.

4- Blossom Drop

While tomato plants love the heat of summer, there is such a thing as too much of a good thing. If night temperatures fail to drop below 80 degrees and if daytime temps reach the mid to high 90s day after day, plants can stop producing flowers or even abort existing flowers. Not much you can do about this one except maybe a few extra church services per week.

5- Too Much Love

Yes, it’s possible. We love to fertilize our tomato plants, and when done right, the plants love it too. But once again, too much of a good thing… If you’re one of those people who loves do dowse your plants in the blue juice of the garden, be careful. Too much nitrogen can grow plants to beanstalk proportions but all that nitrogen favors stems and leaves over fruit. The good thing is that nitrogen doesn’t hang around all that long in the soil. If you’ve overdone it for the first bit of the season just back off (or even stop altogether) and plants will gradually start to bear fruit.

So the moral of the story is, hang in there. While tomato plants are not the easiest on the aspiring gardener, with a little attention to detail you can fill your dinner table with one of the most rewarding bits the garden can offer. Whether it’s a $64 tomato or an inflation adjusted $128 tomato, it’s worth it!

This article was originally submitted to the Courier Journal on June 21, 2022.

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Blurb about Paul here.

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