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. I share in this feeling, so I did some research to find out why it happens.
So, why are your tomatoes growing so slow? Over watering is a common cause of slow growth in tomato plants. Extreme temperatures can also slow the growth of tomatoes. Soil conditions can also have an effect on how quickly your tomatoes grow.
Of course, there are other causes to consider – for instance, the variety of tomato and the time to maturity. Let’s take a closer look at some of the reasons that your tomato plants are growing slowly, and the steps you can take to fix it.
Slow Tomato Growth Due To Over Watering
Over watering is one of the most common causes of slow growth in both young and established tomato plants. When the soil stays moist for too long, it encourages root rot, which destroys the root system of tomato plants over time.
Eventually, the plants will not be able to absorb enough water or nutrients to grow quickly, and they may even die. Let’s look at some ways to address the issue of over watering and get your tomato plants back to health.
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 long to check the weather, and it will prevent you from watering on days when there will be a downpour. If you see cool, damp weather approaching, you can decrease the amount of water for your plants, since it won’t evaporate as quickly in those conditions.
When you do water, make sure that you do it properly. Water your tomato plants deeply and less frequently, rather than giving them a shallow drink every day.
This infrequent, deep watering will encourage stronger, more extensive root systems, and will make the tomato plants hardier. It also gives the soil a chance to dry out between waterings, which helps to prevent root rot.
To tell when to water you 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. Otherwise, leave the plants alone!
Water your tomato plants in the morning if you can. Also, avoid getting water on the leaves, since this can lead to disease.
Instead of using a sprinkler, try using a hose so that you can control the precise amount of water that your plants receive. If hand watering is too time-consuming, you can also set up a drip irrigation system.
Such a system requires some initial setup, but once it is in place, it can save you lots of watering time in the long run.
Address Poorly Draining Soil
Now that you aren’t “killing 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 may end up standing in water, leading to root rot.
Clay soil often 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 compost into the soil.
Compost supplements organic material, 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. Turning your soil with a tiller or shovel can accomplish this, but it may disturb earthworms.
A better way is to turn your soil with a pitchfork, or to use an aerator and avoid turning the soil altogether. When soil contains more air, water can flow through it more easily, leading to improved drainage.
One last method to help 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 and my article on over watering plants.
Slow Tomato Growth Due To Extreme Temperatures
Even if your watering and soil drainage are right on par, extreme temperatures can still destroy your chances of getting a great tomato harvest.
Temperatures That Are Too Cold
When temperatures drop below 55 degrees Fahrenheit at night or 65 degrees Fahrenheit during the day, tomato plants begin to have difficulty producing energy for growth. Unfortunately, you can’t do much to control the weather. However, you can take some steps to protect your plants from the cold.
For smaller plants, use a cloche to protect them from cold, especially if you planted a bit early for your area. For more information, check out my article on how to protect plants from cold.
In the future, make sure to plant your tomato plants at an appropriate time of year, depending on the date of last frost. 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, and transplant them outside when the last danger of frost has passed.
For more established tomato plants, you can use row cover material to protect plants from cold. You can also build a windbreak near your garden to protect plants from the coldest breezes and wind damage.
For more information, check out my article on how to protect your plants from wind.
Temperatures That Are Too Hot
If temperatures get up to 90 degrees Fahrenheit and above, it can slow down the growth of your tomato plants. Unfortunately, there is not much you can do about hot temperatures in a heat wave.
One action you can take is to put mulch on the soil around your tomato plants. This will help to retain water by preventing evaporation due to heat and sunlight. It will also prevent temperature fluctuations in the soil by insulating against heat and sunlight.
If the weather gets really hot and dry, just 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 right. An improper pH, lack of nutrients, or even excessive nutrients can all cause problems for tomato plants, leading to slower growth.
If soil pH is too high or too low in your garden, it can prevent plants from absorbing nutrients through their roots – even if there is plenty of nutrition in the soil! For more information, check out this chart from Research Gate showing the relationship between soil pH and nutrient availability.
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 if your soil pH is off is to do a soil test.
You can buy a soil pH test kit online or at a garden center, or send your soil away to a local agricultural extension.
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.
Excessive or Deficient Nutrients
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.
At the other extreme, an excessive amount of one nutrient can prevent 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 can vary 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 5 feet or less. There are some varieties that stop growing at 2 feet tall! So, if your plant is only 2 feet tall, remember that it may already be up to half of the height that it will ever be.
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 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 (about 6 weeks) in days to maturity may account for the slow growth you are seeing. 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 planted earlier, or he may have different varieties than you.
Other Ways To Speed Up Tomato Growth
If you want to encourage fruit production in your tomato plants, there are a couple of things you can do.
One thing you can do is to prune off suckers – these 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, and you will get fewer but larger tomatoes.
Another thing you can do is to pinch off some of the flowers and 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.
For more information, check out my article on how to pollinate tomato flowers.
By now, you should have a good idea of 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 kill them with kindness!
I hope you found this article helpful – if so, please share with someone who may need the information. If you have any questions or advice about growing tomatoes, please leave a comment below.