You’ve planted your tomatoes and nurtured them every step of the way. It can be disappointing to see them growing smaller and slower than you hoped.
So, why are your tomatoes growing so slow? Over watering is a common cause of slow growth in tomato plants. Extreme temperatures and poor soil conditions can also slow the growth of tomatoes. Certain tomato varieties take longer to grow and mature than others.
Of course, there are other causes to consider. For example, the time to maturity will affect how fast the tomato plant grows and produces fruit.
In this article, we’ll take a closer look at some of the reasons that your tomato plants are growing slowly. We’ll also talk about how to fix the problem or prevent it in the first place.
Why Are Your Tomatoes Growing So Slow?
There are several possible causes of slow tomato plant growth, including:
- Improper Watering – too little and too much will both cause problems!
- Extreme Temperatures – too cold and too hot will both slow down growth.
- Poor Soil Conditions – a pH or nutrient imbalance in the soil will stunt growth.
- Slow Maturing Tomato Variety – some varieties take much longer to mature than others.
Let’s go through these causes one at a time, starting with a common one: improper watering.
Slow Tomato Growth Due To Improper Watering
Improper watering will cause slow growth in tomato plants at any stage of growth.
Under watering is more likely in hot, dry climates or sandy soil. Over watering is more likely in heavy clay soil that does not drain well.
Under Watering Tomato Plants
Tomato plants need plenty of water to grow. Their roots go as deep as 2 feet or more, so they also prefer water that soaks way down into the ground.
Some early signs of under watering in tomato plants include:
- wilting leaves – this is an early symptom. According to the University of Nebraska, plants will recover after watering.
- yellow leaves – this symptom appears later. Without enough water, the plant cannot absorb enough nutrients from the soil.
- dry soil – this may or may not happen for under watered plants, since a plant could wilt on a hot, dry day if its root system is weak.
To tell when to water your plants, use your fingers to feel the soil down to a depth of a few inches. If it feels dry, then you can add water.
If you have a problem with dry soil, you can learn about how to treat it in my article here.
Over Watering Tomato Plants
Over watering is one of the most common causes of slow growth in both young and established tomato plants. It may be even more common than under watering, since many beginner gardeners “do in their plants with kindness!”
When soil stays moist for too long, it leaves no room for air, and the plant’s roots cannot breathe. Over time, this encourages root rot, which eventually destroys the root system of tomato plants.
At some point, the plants will not be able to absorb enough water or nutrients, slowing or stopping their growth. The worst part is that the plants may look under watered, even though the soil is moist.
You can learn more in my article on over watering plants.
Let’s look at some ways to address the issue of over watering and get your tomato plants back on the right track.
Stop Adding Too Much Water
To avoid over watering your tomato plants, make sure to work with Mother Nature, not against her. Check the weather forecast every day for any chance of rain.
It doesn’t take long to check the weather, and it will prevent you from watering on rainy days.
If you see cool, damp weather approaching, decrease the amount of water for your plants. Water will evaporate from the soil more slowly in those conditions, and plants will lose less water due to transpiration (breathing).
Water Plants Deep & Early
When you water tomato plants, make sure that you do it properly. Water them deeply and less frequently, rather than giving them a shallow drink every day.
This infrequent, deep watering will encourage stronger, more extensive root systems. This will make the tomato plants hardier and give it a chance to survive a drought.
Infrequent watering also prevents the soil from staying soggy, which helps to prevent root rot.
Water your tomato plants early in the morning if you can. This gives the sun a chance to dry off the leaves during the day.
Better yet, water from below and avoid getting water on the leaves. Wet leaves can lead to fungal diseases.
Instead of using a sprinkler, use a hose to control the precise amount of water that each plant receives. If hand watering is too time-consuming, you can also set up a drip irrigation system.
A drip irrigation system requires some initial setup, but once it is in place, it can save you lots of watering time in the long run. You can also install a system with a timer to prevent over watering or forgotten watering.
Address Poorly Draining Soil
Now that you aren’t “doing in your plants with kindness” by over watering, it’s time to make sure that the soil is cooperating with your efforts.
If your soil drains poorly, your plant’s roots will end up standing in water, leading to root rot. The University of Missouri Extension has information in this article on how to determine if your soil drains well. or not.
In general, clay soil drains slowly, whereas sandy soil drains quickly, and loamy soil is somewhere in the middle. If your soil drains poorly, one way to remedy the problem is to mix in some compost or aged manure.
Compost will add organic material to soil, which helps to improve drainage. As an added bonus, compost helps to restore some nutrients to the soil.
For more information, check out my article on how to make compost.
Another way to improve drainage is to aerate the soil in your garden. When soil contains more air, water can flow through it more easily, leading to improved drainage.
There are a few ways to aerate your soil:
- Turn your soil with a tiller or shovel – this method will provide aeration, but it may disturb earthworms.
- Turn your soil with a pitchfork – this method is less likely to disturb earthworms.
- Use an aerator – this method avoids turning the soil altogether.
One last method to improve soil drainage is to divert rainwater away from your garden. You can dig trenches and install pipes to direct water away from parts of your garden that tend to flood, which may eliminate the problem of soggy soil.
For more information, check out my article on how to make soil drain better.
Slow Tomato Growth Due To Extreme Temperatures
Even if your watering and soil drainage are excellent, extreme temperatures can still destroy your chances of getting a great tomato harvest.
Temperatures That Are Too Cold For Tomato Plants
When temperatures drop below 55 degrees Fahrenheit (13 degrees Celsius), tomato plants begin to have difficulty producing energy for growth. Colder temperatures will have an even more drastic effect, which you can learn about in my article here.
Unfortunately, you can’t do much to control the weather. However, you can take some steps to protect your plants from the cold.
For younger plants that are still small, use a cloche to protect them from cold, especially if you planted a bit early for your area.
For larger, more established tomato plants, you can use a row cover to protect plants from cold.
You might also want to check out my article on how to protect plants from cold.
In the future, plant your tomatoes at an appropriate time of year, depending on the last frost date. For more information, check out this article from the Old Farmer’s Almanac on last spring frost dates.
If you must start your tomato plants early, try to start them in pots inside your house or greenhouse. Then, transplant them outside when danger of frost has passed.
Temperatures That Are Too Hot For Tomato Plants
If temperatures get up to 86 degrees Fahrenheit (30 degrees Celsius) or higher, it can stop tomato plants from forming fruit or slow their growth.
High temperatures will also prevent tomato fruit from ripening properly. Unfortunately, there is not much you can do about a heat wave.
One action you can take is to put mulch on the soil around your tomato plants when the soil is a bit cooler (in the morning).
This will help to retain water by preventing evaporation due to heat and sunlight. It will also prevent temperature fluctuations by insulating the soil.
You can also try using shade cloth to protect tomato plants from the hottest sun at midday. A piece of shade cloth can lower the temperature for plants by 10 degrees Fahrenheit or more.
If the weather gets really hot and dry, make sure to water your plants more frequently as needed.
Slow Tomato Growth Due To Poor Soil Conditions
Even with proper watering, soil drainage, and temperatures, tomatoes can still be finicky about growing if the soil conditions are not just right.
An improper pH, lack of nutrients, or even excessive nutrients can all cause problems for tomato plants, leading to slower growth.
Improper pH For Tomato Plants
If soil pH is too high or too low in your garden, it will prevent plants from absorbing nutrients through their roots. This can happen even if there is plenty of nutrition in the soil!
Tomato plants prefer a pH in the range of 6.0 to 6.8 (slightly acidic; 7.0 is neutral). The only way to truly know your soil pH is to do a soil test.
You can buy a soil pH test kit online or at a garden center. You can also send your soil away to a local agricultural extension for testing.
For more information, check out my article on how to do a soil test.
If your soil pH is too low (acidic), you can raise it by adding lime (calcium carbonate) to the soil. For more information, check out my article on how to raise soil pH.
If your soil pH is too high (alkaline), you can lower it by adding sulfur. For more information, check out my article on how to lower soil pH.
Do a soil test before adding anything to your soil!
Excessive or Deficient Nutrients For Tomato Plants
If your soil pH is spot on, you may still have deficient or excessive levels of nutrients in your soil. A soil test from a lab can tell you this.
If you provide information on what type of plant you are growing, they can also give you recommendations to treat any problems.
If your tomato plants leaves are starting to turn yellow, check out my article on how to identify nutrient deficiencies.
One common problem that gardeners face is too much nitrogen in soil. This causes plants to add plenty of green growth, at the expense of flowers and fruit.
If your tomato plants are getting tall without any flowers or fruit, excessive nitrogen should be on your radar. For more information, check out my article on over fertilizing and my article on low-nitrogen fertilizers.
Another possible problem is when an excessive amount of one nutrient prevents a plant from absorbing other nutrients. For example, excessive calcium in the soil can prevent a plant from absorbing magnesium, and vice versa.
The reason is that calcium and magnesium have similar chemical properties, so they act in a similar way (they are on the same column in the periodic table). In a sense, these two elements “compete” for uptake by a plant’s roots.
Adding lime will increase the amount of calcium in your soil, and adding Epsom salt (magnesium sulfate) will increase the amount of magnesium in your soil.
For more information, check out my article on whether Epsom salt helps tomatoes to grow.
Be careful about adding anything to your soil until after you have the results of a soil test!
Slow Tomato Growth Due to Variety
Remember that tomato growth rate and maximum size will differ depending on the variety. Let’s look at how each of these factors can affect growth.
Determinate and Indeterminate Tomato Varieties
Determinate tomato varieties stop growing at a certain height, usually at around 5 feet. There are some varieties that stop growing at 1 or 2 feet tall! (you can learn more about Tiny Tim tomatoes on the Victory Seeds website).
So, if your plant is only 2 feet tall, remember that it may already be up to half (or more) of the height that it will ever be. Check the catalog where you got your seeds or plants to find the maximum height for your plant.
Indeterminate tomato varieties don’t necessarily stop growing at a certain height. Sometimes they will fall over, even when staked, due to growing so tall!
Most indeterminate tomato plants will grow to at least 6 feet tall, and some can grow up to 12 feet tall.
If you are growing determinate tomato variety, check its maximum height, and adjust your expectations for plant size accordingly.
Days To Maturity (DTM) For Tomato Plants
Another factor to consider is the days to maturity for tomato plants. Some varieties can mature in as little as 50 days, while others can take 90 days or more to mature.
This huge difference (40 days, or about 6 weeks) in days to maturity may account for the slow growth you are seeing. Check the seed packet to find out the days to maturity for your plants!
Also, remember that the days to maturity is from transplant to harvest – if you start from seed, it will take even longer!
Make sure you are comparing apples to apples, so to speak. If you have tomato plants that take 90 days to maturity, they will probably grow much more slowly than plants with 50 days to maturity.
Also, avoid comparing your tomato plants to your neighbor’s plants. He may have started seeds indoors, transplanted earlier, or planted different varieties than you.
If you want to harvest sooner, you might want to check out my article on vegetables that grow in 60 days or less.
Other Ways To Speed Up Tomato Plant Growth
If you want to encourage growth and fruit production in your tomato plants, there are a couple of things you can do.
One thing you can do is to prune off the suckers. Suckers are side vines that grow off the tomato plant, which eventually grow fruit.
If you prune some of the suckers off, the plant will have more energy to devote to flowers and fruit. You will get fewer but larger tomatoes.
Another thing you can do is to pinch off some of the flowers. Then, hand-pollinate the remaining flowers.
Again, this allows the plant to focus its energy on fewer tomatoes, leading to larger fruit. You can use an electric toothbrush or other methods to hand pollinate tomato flowers.
Now you know the common causes of slow tomato growth, along with ways to remedy the situation. Be sure to pay attention to water, temperature, and soil conditions, and don’t do in your plants with kindness!
If you find your tomatoes growing slowly and wilting, bacterial wilt may be to blame – you can learn more about it in my article here.
I hope you found this article helpful – if so, please share with someone who may need the information.