Why Are My Tomato Plants Growing So Tall? Do This To Fix It!


Sometimes, your tomato plants seem to grow at a pace that is completely out of control.  I have seen this happen in my garden before, and you may also be seeing it in your garden this year.  You are probably also wondering, just as I did, why this tall growth of tomato plants happens.

So, why are your tomato plants growing so tall?  Tomato plants will grow tall and thin (spindly) due to a lack of sunlight.  Tomato plants will also grow tall without flowers or fruit due to over fertilization, especially when high levels of nitrogen are present.  Finally, tomato plants will grow tall if you have planted an indeterminate tomato variety (some can reach heights of 9 feet or taller!)

Of course, there are ways to prevent the problem of extremely tall tomatoes.  If you are already experiencing this problem in your garden, there are ways to fix it without losing your crop.  Let’s take a closer look at why tomato plants grow so tall, and the steps you can take to address the problem in your garden.

Why Are My Tomato Plants Growing So Tall?

As mentioned before, tomato plants can grow tall due to a lack of sunlight, over fertilization due to excessive nitrogen, or simply because they are an indeterminate variety.  Let’s start off by examining what happens when tomato plants experience a lack of sunlight, and how to solve this problem.

Your Tomato Plants Are Tall And Thin Due To A Lack Of Sunlight

According to the University of New Hampshire, tomato plants require full sunlight, growing best in areas that receive full sun for most of the day.

sunlight through forest
Tomato plants need full sunlight, so they may grow tall and thin (spindly) when trying to reach for the light if they are not getting enough of it!

If your tomato plants are not receiving enough sunlight during the day, they will grow “spindly” (tall and thin) instead of thick and strong.  This happens because the plant is stretching itself out to grow as tall as possible.

This can happen if there is not enough sunlight getting to the plant in its current location.  It can also happen if other nearby plants are blocking sunlight from the tomato plant.

You don’t want your tomatoes to grow spindly, since this will decrease the tomato yield at harvest time.  So how can you prevent tall and spindly tomatoes?

First, plan ahead and check the location of your garden to make sure your tomato plants will get enough sunlight during the entire growing season.

If there are any trees directly overhead, trim the branches or cut down the entire tree.  If that is not practical, then consider moving the tomatoes to another spot in your garden.  You can even move the entire garden to a brighter spot in your yard to take advantage of more hours of sunlight.

Also, make sure that your garden is not too close to a house, barn, or garage.  Otherwise, the structure can block sunlight during the day and cause your tomato plants to grow tall and spindly.

Finally, you should regularly check the amount of sunlight your tomato plants are getting during the growing season.  If there are taller, leafy plants nearby (including other tomato plants!), they may be competing with the tomatoes by blocking some of their sunlight.

To prevent this problem, be sure to use adequate spacing between tomato plants.  The spacing for tomato plants will vary depending on the variety, but a good general rule is 1 to 3 feet (30 to 91 centimeters) between plants, with more space between rows.

tomato stakes
Remember to leave enough space (1 to 3 feet) between your tomato plants. The distance will depend on the variety, so check the seed packet or catalog to make sure.

For more information, check out this article from on tomato plants from the University of New Hampshire Extension.

Your Tomato Plants Are Tall Without Flowers Or Fruit Due To Over Fertilization

Tomato plants may grow very tall if they are over fertilized, especially with nitrogen-rich fertilizers.  The idea is that the nitrogen (the “greening nutrient”) causes the stems and leaves to grow large and thick, at the expense of flowers or fruit.

tomato flower
Excessive nitrogen can cause tomato plants to produce lots of green while neglecting to produce fruit. Of course, you should also make sure proper pollination is happening!

This sometimes makes for a tall tomato plant with few flowers or fruit.  Of course, a lack of fruiting can be due to inadequate pollination.  For more information, check out my article on how to hand pollinate tomato plants.

You can also try blossom set spray, which causes flowers to set fruit, even if pollinators are nowhere to be found.  You can check out blossom set spray on the Gardener’s Supply Company website.

To avoid the problem of over fertilization, try using low-nitrogen fertilizers for your tomato plants.  For more information, check out my article on low-nitrogen fertilizers.

Your Tomato Plants Are Tall Because They Are An Indeterminate Variety

This is a common problem, since indeterminate tomato varieties will grow as long as they are able to do so (generally until the first frost of the season).  In an area with a long growing season, this means that some indeterminate tomato plants will reach a height of 10 feet or even taller!

This makes it difficult for anyone to harvest the fruit on the top part of the plant.  It also makes it more likely that the plant will fall over in the wind, or due to the weight of its own stem, branches, and fruit.

Luckily, there are several solutions for this problem – you can use some or all of these ideas as the situation warrants.

Let Your Indeterminate Tomatoes Grow Up And Then Down

If your tomato plants are growing too tall, then simply double the amount of space they have available to grow!  Let them climb up one side and down the other side of an arbor.

An arbor is a garden feature that is often used at the entrance to a garden.  However, you can place an arbor anywhere in your garden and allow your tomato plant to grow up and over the structure.

arbor arch
An arbor can create a “living arch” in your garden, and you can use it to support indeterminate tomatoes so that their height does not get out of hand.

This makes it much easier to harvest any fruit on the uppermost branches.  For more information, check out my article on arbors.

You can also let your tomato plants grow up and over an A-frame trellis.  An A-frame trellis serves the same purpose as an arbor, but with a pointed top instead of a flat or arched top.

For more information, check out my article on trellises.

As an added bonus, you can plant shorter, shade-tolerant plants (such as lettuce or spinach) beneath the arbor or A-frame.  This will save space in your garden and allow your plants to help each other to grow!

Provide Taller Supports For Your Indeterminate Tomato Plants

You can also use taller stakes instead of cages if you need more height to allow your tomato plants to grow.  Remember that cages are more useful for determinate tomato plants that only grow to a height of 3 to 5 feet.

tomato stakes
Indeterminate tomato plants will need tall stakes for support – tomato cages are generally insufficient for such tall varieties.

Also, remember that you will need to drive a good portion of the stake into the ground to keep it steady, so that it does not fall over from the weight of the tomato plant.  This means that you will want a 10-foot tall stake, driven 2 feet into the ground, in order to give a tomato plant 8 feet of pole to climb.

For more information, check out my article on how to support tomato plants.

Prune (Top) Your Indeterminate Tomato Plants

Sometimes, even the use of arbors, A-frame trellises, and tall stakes are simply not enough.  Your indeterminate tomato plants may just be too tall, and you cannot give them the space they need to grow.

In that case, you can “top” them, or prune the top part of the plant away, to prevent them from falling over after they outgrow their supports.  Topping prevents the tomato plant from getting too tall.  As an added bonus, you can make new plants out of the trimmings from the trimmed tops of the plants.

In order to top your tomato plant, cut off the top part of the main vine (the part that is growing higher than you would like).  You may be able to snap off the top of the stem using your fingers and hands.

If not, sanitize a knife or pruning shears with alcohol to use for cutting.  Clean the knife or shears with alcohol between each new cut, to avoid spreading disease between your plants (better to be safe than sorry!)

pruning shears
If you use pruning shears to top your tomato plants, be sure to clean thoroughly with alcohol between cuts to avoid the spread of diseases.

One important thing to remember is that you should not remove too many leaves at once when pruning your plant.  Otherwise, you might expose the fruit on the tomato plant to sunscald.

Sunscald occurs when intense direct sunlight causes white or yellow spots on the fruit of tomatoes (or peppers).  For more information, check out this article about sunscald on the Joe Gardener website.

Finally, if you want to get new tomato plants from this topping exercise, simply plant the trimmings deep in the soil to create new plants.

For more information, check out my article on why to plant tomatoes deep in the soil.

Conclusion

By now, you have a much better idea of why your tomato plants are growing so tall.  You also know how to prevent the problem, and how to treat it if it is already happening this year.

I hope you found this article helpful – if so, please share it with someone who can use the information.  If you have any questions about tomato plants that grow tall, please leave a comment below.

Want more information about growing tomatoes? Check out my article on the top mistakes to avoid when growing tomatoes.

jonathon.david.madore

Hi, I'm Jon. Let's solve your gardening problems, spend more time growing, and get the best harvest every year!

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