Why Tomato Plants Grow Tall | Top 5 Reasons and How to Stop Them

Tomato plants will grow tall if you choose large indeterminate varieties. These include Beefsteak, Grosse Lisse, moneymaker and heirloom varieties such as Reisetomate. Tomato plants that are getting too much water, nitrogen or not enough sunlight. This can lead to tall, leggy tomatoes that can bend or break easily.

This article will explore why tomato plants grow tall and what you can do to stop them from growing once they reach the ideal height for you.

Why Tomato Plants Grow Tall

Check to the top reasons why tomato plants grow tall and how you can stop your tomato plant from getting out of control.

1. Choosing large indeterminant varieties

The top reason why tomato plants grow tall is due to the variety you choose. Indeterminate tomato varieties grow like a vine continuing to grow upwards from the top stem. They can send out side shoots from their main stem and grow flowers and fruit all the way up.

Large varieties like beefsteak and grosse lisse can easily grow over 6 feet. If they are given the room they need they will continue to grow like a vine sending up new leaves and flowers from the stem.

Funky indeterminant heirloom tomato varieties will grow tall with interesting fruit.

2. Good growing conditions

Tomato plants will grow tall rapidly when they get the right environment. This includes at least 6 hours of sunlight, warm days, warm soil, minimal wind and well-draining soil rich in organic matter.

This is a good thing giving you a large, healthy plant that will produce a lot of tomatoes.

Tomatoes that are watered regularly in perfect growing conditions can grow rapidly from 2-3 inches to over 6 feet in 8 weeks.

I am growing large indeterminant varieties like money maker and grosse lisse which have grown to this size over spring.

They have easily reached the top of my 5 foot high stake and are starting to bend over due to the weight of the tomatoes and the stems.

This bent tomato stem can be saved by trimming off the excess growth at the end and tyeing it back up up to the stake.

Once they reach the top you can prune the stems to keep them at the height you want without damaging the plant.

Tomatoes will grow new stems from growth nodes further down the stem once their top growth is removed.

3. Excess nitrogen in the soil

Planting tomatoes in soil that has loads of nitrogen will encourage them to grow large fast. They will add lots of stem length and leaves.

Soil that has had lots of high nitrogen animal manures like chicken or sheep manure added will

If you add a lot of nitrogen based fertilizer this will also cause the plants to grow tall and large.

My tomatoes are over 6 feet tall now and covered in fruit.

It is best to avoid planting tomatoes in soil that has excess nitrogen as you may end up with plants with lots of leaves and minimal flowers and fruit.

To encourage the plant to grow flowers and fruit there needs to be higher potassium and phosphorus to nitrogen ratios. You can stop adding fertilizer to the tomatoes 4 weeks after planting.

If you are still not getting fruit and flowers you can add a fertilizer that is higher in phosphorus and potassium to encourage fruiting.

4. Lack of sunlight

Tomatoes can grow very tall and leggy if they are lacking sunlight. Tomatoes will grow long stems that become weak as they grow if they are not getting the sunlight they need.

Tomato plants need loads of sunlight over their growing period to encourage strong stems and lots of fruit. Plants will reach their stems up to reach any light available if they are planted in low light conditions.

Plant tomatoes in a position that gets 6 hours or more of sunlight per day. The more sunlight they get the stronger their stems will be and the more fruit they will produce

They can still grow tall but will be strong enough to hold the fruit they produce.

My tomato plants are covered in fruit. This tomato has been nibbles by bugs but will still be fine to eat.

5. Overwatering

Tomato plants that get too much water can often grow tall and leggy. They will often develop light green stems or even yellowing leaves.

Overwatering will encourage rapid growth, but the stems will be weak and can bend. Overwatering can also encourage fungal root rot which can eventually kill the plant.

It is ideal to water tomatoes when the top inch of the soil is dry. In spring this can be every few days, in summer this may be as often as every day. Add mulch to the soil to avoid the need to water too often.

How to stop tomatoes from growing too tall

Check out these easy ways to stop yoru tomatoes from growing too tall at home.

Pinch off the top growth

The best way to stop your tomatoes from growing too tall is to pinch off the top growth. Once tomato plants have reached the height you want them to, pinch or snip off the top 1-2 inches of growth. This will stop the stem from growing.

Pinch the stem off near a growth node to avoid a long stem dying back on the top.

You may notice small stems growing from the sides near the near the node that you pinched back to. You can either leave these to grow or pinch them off again.

You can use secateurs to remove longer parts of the stem if they have grown too tall. Cut just above a growth node.

Once you pinch of the top growth, most tomato varieties will grow new stems from further down. This can mean that you will get more flowers and fruit from the side branches.

Determinant tomatoes will grow new flowers and fruit further up the stem. They can also produce fruit on new stems that come from the side of the plant.

Removing the top of the stems or ‘topping’ tomato plants will stop them from growing too tall.

Choose determinant tomato varieties

For a smaller, bushier tomato look for determinant varieties. Roma tomatoes are a perfect example as they will grow, small, bushy and will grow tomatoes all over the plant. These tomato varieties tend to grow their tomatoes all at once so you will have a big harvest you can turn into sauce.

Choose dwarf tomato varieties

You can also look for dwarf varieties of tomatoes or bush cherry tomatoes. These will grow smaller, denser will need less vertical space to grow.

Why Tomato Plants Grow Tall | Summary

Which tomato plant variety you choose is important as it will determine how big your tomato will grow. If you have a small vertical space, look out for a determinant or bush variety. If you want to grow a determinant vine variety, just pinch off the top of the vine once it reaches the desired height.