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Over the last 10 years, I have grown countless different fruit and vegetables from the staples like cabbages and beans to the more exotic ones like kohlrabi and Cape Gooseberries. However, there are a few plants I am never without, and one of those is the tomato plant.
Every year I grow 4 or 5 different varieties of tomato, just to keep my salads interesting. I must have grown over 1,000 tomato plants in my life.
Even so, I occasionally find myself with one or two tomato plants that have started to dry up and die. It can be incredibly frustrating. In this article I consider why tomato plants dry out, and what we can do to prevent it from happening.
Tomato plants can dry out and die for several reasons, but the main 3 reasons are due to underwatering or watering incorrectly, diseases such as verticillium wilt or Fusarium wilt, and poor root or stem development due to lack of available nutrients.
Why Do Tomato Plants Dry Up?
In my experience of growing tomatoes, by far the most common reason for tomato plants to dry up is thanks to underwatering, or incorrect watering.
To produce a good crop of tomatoes, most of us have to grow our tomato plants either in a sunny location (if we live in a warm climate) or undercover in a greenhouse or polytunnel.
As such, these plants naturally find themselves in locations where they are warm and baked by the sun.
Needless to say, any plant that is grown in such a location will need to be well watered. Tomato plants can grow large, and producing their fruits requires a lot of water, making tomato plants even more susceptible to drying out.
To make matters worse, once the tomato plant starts producing fruit, the plant needs to be watered consistently to prevent the fruits from splitting.
How much water do tomato plants need?
‘How much water do tomato plants need?’ is a tricky question to answer because there are so many variables. How big is the plant? What sort of soil is it growing? How many fruits is the plant developing? The questions go on.
However, as a rough guide, I try to give each of my tomato plants around 1-gallon (3.5 liters) of water 2 to 3 times a week, and I usually give it to them in the morning before the sun is at its strongest.
Essentially I have a 2-gallon (7 liters) watering can, so I give each plant around half a can. Don’t get too caught up in the exact quantity of water you give each tomato plant, just make sure the ground never dries out. Adjust your watering depending on local conditions.
How should you water tomato plants?
How one should water their tomato plants is easier to answer than how much they should water. Tomato plants want consistent watering.
In fact, your tomato plants will need less water if they are watered consistently compared to if they are watered infrequently.
The best way I have found to water my tomato plants is to use a plant pot submerged in the soil about 4″ (10cm) away from the stem of the tomato plant.
Using a submerged pot helps gauge roughly how much water you are giving your tomato plants, allowing you to be consistent and also helps reduce water runoff.
Sometimes, especially if the soil is already dry, when we water our plants, much of the water runs away before soaking into the soil. Using submerged pots prevents this.
Other Reasons Tomato Plants Dry Out
It is possible that you are watering sufficiently and consistently, yet your tomato plants are still drying up and dying.
If this is the case, the next most likely cause is a tomato plant pest or disease.
Diseases such as Verticillium wilt and Fusarium wilt, are probably the two most frequently seen diseases that cause tomato plants to die back. Both are caused by a fungus that lives in the soil.
Verticillium wilt and Fusarium wilt both attack the vessels in the tomato plants that carry water around the plant, reducing the tomato plant’s ability to draw water into its stem, and leaves.
If your tomato plants are affected by either of these fungi, the leaves will usually turn yellow before becoming brown and the plant stems will begin to shrivel and wilt.
To the best of my knowledge, there are currently no chemical treatments for either fungus.
Watch: Tomato Problems Part 3: Wilt Diseases
As well as plant diseases, there are some pests that can cause your tomato plants to dry out and die.
Ants are one of the most common culprits. If ants decide to build their nest directly under a tomato plant, which is what happened to me last year, the first you might know about it is when one of your tomato plants begins to dry out.
I had a nice row of tomato plants that were beginning to flower and set fruit. Out of nowhere, one plant began to shrivel up. It turned out an ant colony was living directly below the tomato plant.
Whilst the ants themselves do not affect the tomato plant, the disturbance to the soil around the plant’s roots meant the tomato plant could not take up sufficient water.
In this instance, there was not a great deal I could do. I just pulled up the affected plant and left the ants to get on with life. I considered churning the soil to move the ants on, but I did not want them making their home under another one of my tomato plants.
Poor root development
Poor root development or a general lack of nutrients available in the soil can also cause tomato plants to dry up and die.
The first few weeks of a tomato plant’s life are incredibly important as that is when the initial root structure forms. If this structure does not form correctly, the tomato plant will never grow to its full potential.
A lack of available nutrients in the soil, either when the seedlings are first developing, or even once the tomato plant is more mature, can mean the vessels inside the tomato plant stem and leaves do not develop properly, meaning the roots can not supply the tomato plants with sufficient water to grow and develop fruit.
The best way to prevent poor root development is to always grow your tomato seeds in fresh, good-quality seed compost such as this one that I recently ordered from Amazon.
Once your tomato plants are ready to be planted into the ground, ensure the soil you are planting them in has lots of well-rotted manure or compost dug into it.
How To Prevent Tomato Plants Drying out?
By far the best way to prevent tomato plants from drying out is to grow them in humus-rich soil that will retain moisture.
If your current soil is dry and dusty or sandy, consider digging in plenty of well-rotted manure or compost. Both manure and compost help the soil retain moisture.
Once your tomato plants are growing, water them well and on a regular basis. About once every two or three days is right in most situations, but if you live in a very hot, dry climate, you might sometimes need to water daily.
Using pots submerged in the ground next to each tomato plant is the best way to gauge how much water you have given each plant and a great way to avoid water runoff around the plants.
Keep a close eye out for any pests or diseases that may be affecting your tomato plants, and take swift action at the first signs of a problem.