Why Are My Tomato Plants Growing So Tall? (3 Things You Should Know) | GreenUpSide (2024)

Sometimes, young tomato plants grow tall and thin, stretching themselves out. Other times, they 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.

So, why are your tomato plants growing so tall? Young tomato plants grow tall and thin (spindly) due to lack of sunlight. Tomato plants also grow tall without flowers or fruit due to over fertilization, especially with high nitrogen levels.Tomato plants grow tall if you plant an indeterminate variety (some can reach heights of 9 feet or more!)

There are ways to prevent the problem of extremely tall tomatoes.If you already see this problem in your garden, there are ways to fix it without losing your crop.

In this article, we’ll take a closer look at why tomato plants grow so tall. We’ll also give you the steps you can take to address the problem in your garden.

Let’s get started.

(If you like, you can also watch a video version of this article on Youtube or below).

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Why Are My Tomato Plants Growing So Tall?

As mentioned before, tomato plants grow tall for a few reasons, including:

• lack of sunlight (often leads to leggy tomato plants or stretched out seedlings as they try to reach more light)
• over fertilization (usually due to excessive nitrogen)
• planting an indeterminate variety (indeterminate tomato plants grow much taller than determinate varieties)

The table below summarizes the three main causes of tall tomato plants and when you might see it happen.

Let’s do some digging to find out just how tall tomatoes grow. Then we’ll get into how you can prevent or fix the problem of tall tomato plants.

How Tall Do Tomato Plants Grow?

The average height of a tomato plant depends on the type. Many determinate tomato varieties grow 5 feet tall at most, while indeterminate tomato varieties can grow to a height of 8 feet or taller!

Tomato plant height can vary quite a bit between different types. How high tomato plants grow also depends on the care you provide (environmental conditions) and pruning (more on this later!)

For example, Tiny Tim tomato plants only grow to 1 foot tall, while the Guinness Book of World Records suggests that the tallest tomato plant was 65 feet tall!

You can learn about all kinds of micro dwarf tomatoes (that only grow to a height of 1 foot!) in my article here.

Remember:

• indeterminate tomato varieties grow taller and produce fruit for a longer harvest window (you can find a list of indeterminate tomato varieties here)
• determinate tomato varieties do not grow as tall and produce fruit all at once, in a short harvest window (you can find a list of determinate tomato varieties here).

You can learn more about the difference between the two types of tomatoes in this article.

It might be that your tomato plants are tall due to the variety you have chosen. But, that might not be the only reason.

Tomato plant height is affected by several other factors as well.

Let’s take a look at what can cause tomato plants to grow tall (and how you can address the issue).

Your Tomato Plants Are Tall & Thin Due To A Lack Of Sunlight (Leggy Tomato Plants)

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

If your tomato plants are not receiving enough sunlight during the day, they 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 (to reach more light).

This will happen if there is not enough sunlight reaching 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 plants to grow spindly, since will reduces your tomato yield.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 (wood chips make a good mulch for garden paths to prevent weeds!)

If that is not practical, consider moving the tomatoes to another spot in your garden.You can move the entire garden to a brighter spot in your yard to take advantage of more sunlight hours.

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

Finally, check often to see the amount of sunlight your tomato plants are getting. 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.

A good general rule is 1 to 3 feet (30 to 91 centimeters) between plants, with more space between rows. This space leaves room to water, fertilize, harvest, and prune tomato plants during the season.

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

This makes for a tall tomato plant with few flowers or fruit.A lack of fruiting can be due to inadequate pollination too.

You can try to attract bees in your yard to improve pollination. You can also hand pollinate your tomato plants to help with fruit production.

(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.

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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, this means that they will keep growing 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 8 feet or even taller!

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

How To Keep Tomato Plants Short

Luckily, there are several solutions for the problem of tall tomato plants. You can use some or all of these ideas, depending on your situation.

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.But you can put an arbor anywhere in your garden and allow your tomato plant to grow up and over the structure.

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.

If you have a wall to mount it against, an ordinary trellis can also help to support your tomato plants. Here are two trellis options from Ace Hardware:

• Panacea Brown Wood 72 inch Trellis
• Panacea Black Steel 72 inch Trellis

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.

Also, remember that you will need to drive a good portion of the stake into the ground to keep it steady. Otherwise, you run the risk of the entire stake falling over due to 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. This will prevent them from falling over after they outgrow their supports.

Topping tomato plants prevents the tomato plant from getting too tall.As an added bonus, you can make new plants by planting the trimmings from the 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!)

Remember: do 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 plants after topping a tomato, simply plant the trimmings deep in the soil to create new plants. Tomato plants can grow new roots from their vines, so you can bury them deeper than you think.

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

When To Top Or Prune Tomato Plants

A good time to top or prune tomato plants is when the growing tip (highest part) of the plant reaches the top of the support (stake, cage, or trellis). Topping or pruning is a good way to reduce vine height if you want to keep your tomato plants short.

If you are trying to keep your tomato plants neat, you can remove suckers by pruning any time they appear. This will help to prevent bushy tomato plants and make them much easier to care for and harvest from.

Conclusion

The table below summarizes the scenarios when you might see tall tomato plants and what causes it.

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 keep tomato plants short.

You can learn what to do with tall plants here.

If your tomato plants are too tall with no fruit, check out this article on why it happens (and how you can fix it).

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

If you want to learn some interesting facts about tomatoes, check out my article on where tomatoes are from.

I hope you found this article helpful – if so, please share it with someone who can use the information.

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