Common Mistakes When Growing Tomatoes (Don’t Do This!)

There are plenty of mistakes to be made when growing tomatoes in your garden.  This is especially true if you are a first-time tomato grower, but I think a list could help even experienced gardeners to know what to avoid.

15 Common Mistakes When Growing Tomatoes

To save you some time and aggravation, I’ve put together a list of 15 common mistakes that gardeners make when growing tomatoes.  Hopefully, this list will keep you from having to make any of these tomato growing mistakes yourself.

Common Tomato Growing Mistake #1: Choosing The Wrong Tomato Variety

Before you ever plant a single seed or water a single drop, you need to choose the right tomato variety for your garden.  To make the right choice, think about things like the temperature and length of the growing season in your area.

tomato seedling
Before you even plant a seed, you should make sure you choose the right tomato variety for your area.

Heat-Tolerant Tomato Varietiesin

If you live in an area where temperatures often soar to 90 degrees Fahrenheit (32 degrees Celsius) or higher, then choose a heat-tolerant tomato variety, such as:

For a more extensive list, check out this catalog of heat-tolerant tomatoes on the Bonnie plants website.

Fast-Maturing Tomato Varieties

If you live in a region with a short growing season (such as the Northern U.S.), then choose a fast-maturing tomato variety, which will allow you to avoid late spring frosts and early fall frosts.

Some tomatoes can take as long as 123 days to grow from seed to ripe fruit.  However, there are others that can produce ripe fruit in 49 days (7 weeks) if you transplant them as seedlings.

Here are some fast-maturing tomato varieties:

early girl tomatoes
Early Girl tomatoes mature quickly compared to other tomato varieties. Image from:

For more information on times to maturity, check out my article on when tomato plants produce fruit.

Disease-Resistant Tomatoes

Finally, you will want to choose disease-resistant tomatoes, especially if you have had a problem with diseases in your garden in the past.

tomato early blight
Early or late blight can put a damper on your tomato harvest for the season.

Seed catalogs will indicate disease resistance of tomato plants.  Some common tomato diseases to look out for include:

  • Fusarium wilt
  • Verticillium wilt
  • Alternaria Stem Canker
  • Early blight (can be spread from potatoes)
  • Late blight (can be spread from potatoes)

For more information, check out my article on how tomatoes get blight, and my article on the top 10 blight resistant tomatoes.

Common Tomato Growing Mistake #2: Planting Tomatoes Too Early Or Too Late

Tomato plants prefer warmer soil temperatures, and they need soil to be at least 55 to 60 degrees Fahrenheit (13 to 16 degrees Celsius) in order for seeds to germinate.

For more information, check out this article on ground temperatures for planting tomatoes from the Cooperative Extension.

If you want to get ahead of a short growing season, you can start tomato seeds indoors 6 to 8 weeks before the last spring frost date.

For more information, check out this article from the Old Farmer’s Almanac on growing tomatoes.

Even if you start your seeds indoors, you still need to avoid late spring frosts, which can kill tomato seedlings.

To find the last spring frost date for your area, check out this frost date calculator from the Old Farmer’s Almanac.

At the other end of the growing season, you need to make sure your tomatoes will ripen so that you can harvest before the first fall frost.  The link above will tell you the last spring and first fall frost dates for a given area.

For more information, check out my article on when it is too late to plant tomatoes.

Common Tomato Growing Mistake #3: Not Using Crop Rotation

Crop rotation simply means that you do not plant the same crop in the same place in your garden every year.  Instead, you alternate between different crops on a 2, 3, or 4 year rotating schedule.

For example, in one area of your garden, you might plant tomatoes the first year, carrots the second year, broccoli the third year, and beans the fourth year.  Then, rotate back to tomatoes and start again.

For more information, check out this article on crop rotation from Wikipedia.

Keep in mind that it will not do to rotate tomatoes with related crops, such as potatoes, peppers, or eggplants.  The main reason is that they share many of the same diseases.

jalapeno pepper plant
Peppers and tomatoes share some of the same diseases in common, so avoid planting them in the same spot two years in a row.

For example, potatoes and tomatoes are both affected by early and late blight.

Common Tomato Growing Mistake #4: Allowing Soil To Become Depleted

Tomatoes and other plants will use nutrients in the soil as they grow during the season.  Over time, this will cause the soil to become depleted (lacking in nutrients), even if you use crop rotation.

The best solution for this problem is to add compost to your garden soil.  Compost is what you get when you let yard and kitchen waste (grass clippings, banana peels, leaves) decompose.

compost bin
Compost is a great way to recycle yard and kitchen scraps while adding nutrients and organic material to your garden.

For more information, check out my article on how to make your own compost.

To give an added boost to your soil, you can mix manure (animal waste and bedding) into your compost.  Just make sure to let it decompose completely before mixing it into your garden.

For more information, check out my article on where to get manure for your garden.

Common Tomato Growing Mistake #5: Nutrient or pH Imbalances In Your Soil

You may have difficulty growing tomatoes (and other crops) if your soil is too acidic or too basic.  Both of these conditions can prevent plants from absorbing the nutrients they need from soil.

The best way to determine soil pH is with a soil test.  For more information, check out my article on how to do a soil test.

The ideal soil pH for tomato plants is 6.0 to 6.8 (slightly acidic to neutral).

If your soil is too acidic (pH is too low), you can add lime (calcium carbonate) to raise the pH.

If your soil is too basic (pH is too high), you can add sulfur to lower the pH.

Remember: always perform a soil test before adding anything to your soil!  Otherwise, you may be making a problem worse.

Even if the soil pH is in an acceptable range, you may still have a deficiency of some nutrients.

For instance, a lack of calcium in the soil can lead to calcium deficiency in plants.  In tomatoes, this can lead to blossom end rot, which appears as a brown spot on the bottom of the tomato fruit.

These tomatoes have blossom end rot, the result of calcium deficiency.

Again, a soil test is the best way to tell if you have any nutrient deficiencies in your soil.

Common Tomato Growing Mistake #6: Lack Of Sunlight For Your Tomato Plants

Tomatoes need full sun to grow their best, which means 8 hours of sunlight per day.  As such, you should not plant tomatoes too close to your house, garage, or shed, especially on the north side of a building.

sunlight through forest
Tomatoes need full sun, so don’t plant them near a tree line!

You should also avoid planting tomatoes near a tree line or underneath a tree with a large canopy.  There might be enough sun under a tree in April or May, but things can change once the leaves start to grow in!

Finally, if you are growing tomato plants in containers indoors, be sure to put the container close to a south-facing window so that it gets plenty of sunlight for growth.

Common Tomato Growing Mistake #7: Forgetting To Harden Off Tomato Seedlings

When you harden off tomato seedlings, you are helping them to get used to outside conditions.  After starting from seed indoors, the plants are used to growing in perfect conditions.  After all, the levels of light, temperature, and humidity are fairly well controlled in your house.

After easy living indoors, being placed outside in the cruel world can be a real shock to your tomato plants!  To make the transition easier, gradually expose them to more time in the sunlight, wind, and rain.

tomato seedling
Be sure to harden off your tomato seedlings to help them get used to life on the outside.

A greenhouse or cold frame is a great way to help your young tomato plants to make the transition to outdoor conditions.  If a frost threatens, you can use cloches or row covers to protect your tomato plants.

For more information, check out my article on how to protect your tomato plants from cold and frost.

Common Tomato Growing Mistake #8: Planting Tomatoes Too Close Together (Crowded Spacing)

There are many problems that can occur when you put tomato plants too close together.

First of all, overcrowding can result in extreme competition for water and nutrients in the soil, and even for sunlight.  If you plant your tomatoes too close together, you will end up with many small plants with little or no fruit.

Instead, give them plenty of space (2 feet apart) so that you have fewer but healthier plants that will produce lots of fruit.

Overcrowding also makes it much easier for diseases and pests to spread from one tomato plant to the next.  If the leaves of two plants are touching, the spread of pests and diseases is even more likely.

In some cases, you may get “volunteer” (unplanted) tomato plants if you grew tomatoes in your garden in prior years.  It may seem cruel, but it is probably a good idea to pull out these volunteers and transplant them elsewhere or destroy them.

The reasons are the same as above: too many tomato plants in an area will lead to overcrowding and competition for resources, and also allow diseases to spread faster.

For more information, check out my article on volunteer tomato plants.

Common Tomato Growing Mistake #9: Not Supporting Your Tomato Plants

Before you get the wrong idea, I am not talking about encouraging your tomato plants to pursue their dreams.  I am talking about using cages, trellises, or stakes to help them to grow tall and straight.

There are plenty of good reasons to do this, including saving ground space in your garden, preventing disease, and making it easier to water, fertilize, prune, and harvest.

Determinate tomato varieties tend to be shorter, and tomato cages are a good choice to support them. 

plant cage
A tomato cage is a great way to support determinate tomato plants, which tend to be a bit shorter.

For more information, check out my article on tomato cages.

Indeterminate tomato varieties tend to be taller, and trellises or stakes are a good choice to support them.  For more information, check out my article on trellises and my article on supporting tomato plants.

tomato stakes
Tomato stakes are a tried and true method of supporting indeterminate tomato plants, which tend to grow taller (easily 6 feet or more!)

Common Tomato Growing Mistake #10: Not Using Mulch Around Your Tomato Plants

Mulch serves many useful purposes in your garden.

wood chip mulch
Mulch can insulate soil and prevent rapid water loss due to evaporation.

First of all, mulch acts as insulation, preventing your soil from getting too hot or too cold as temperatures fluctuate.  This is useful when a hot, humid, sunny day is followed by a cool, rainy night.

Mulch can also help to regulate moisture in the soil.  Mulch prevents the sun from heating up the soil, which keeps water from evaporating.  This can save your tomato plants in drought conditions or when watering bans are in effect.

Common Tomato Growing Mistake #11: Over Watering Or Under Watering Your Tomato Plants

Inconsistent watering is another cause of blossom end rot in tomato plants, so be sure to water consistently.  Avoid letting the soil stay dry for too long.

If you find that you have a problem with dry soil, check out my article on how to treat dry soil.

On the other hand, over watering your tomato plants (or any plants for that matter) can lead to root rot and eventual death.  The best way to decide when to water is to feel the soil with your fingers.

garden hose
Avoid over watering or under watering your plants!

If the soil feels dry 2 or 3 inches below the surface, then go ahead and water.  Keep an eye on the weather, and avoid watering heavily before a rainstorm.

For more information, check out my article on over watering your plants.

Common Tomato Growing Mistake #12: Over Fertilizing Your Tomato Plants

There are some cases where compost alone will not provide enough of the nutrients your plants need.  In those cases, it is ok to use some fertilizers to supplement what is lacking.

However, remember that it is possible to harm or kill your tomato plants by over fertilizing them.  For example, too much nitrogen can prevent your tomato plant from producing any fruit.

For more information, check out my article on over fertilizing and my article on low-nitrogen fertilizers.

Common Tomato Growing Mistake #13: Lack Of Pollination For Tomato Flowers

Tomato plants are self-pollinating, but self-pollination does not mean guaranteed pollination.  Tomato plants still need help from pollinators (such as bees), wind, or humans.

Normally, bees and other pollinators will travel from flower to flower, collecting nectar.  The buzzing of a bee’s wings stimulates the male part of a tomato flower to release pollen onto the female part.

If all goes well, the flower will produce fruit.  However, there are several things that can go wrong.

If humidity is too high, the pollen will stick to the male part of the flower, and won’t be released properly.

If humidity is too low, the released pollen will not stick to the female part of the flower.

If temperatures are too cold or too hot, bees will not be out working, and so pollination will not occur.

bee on blueberry flower
Bees will not do their pollination work if it is too hot or too cold.

If the air is still, even the wind won’t be able to help with pollination.

If this “perfect storm” of pollination problems occurs in your garden, don’t worry: you still have an option.  You can pollinate your tomato plants by hand, using an electric toothbrush, paintbrush, or other tool.

For more information, check out my article on how to hand-pollinate tomato plants.

Common Tomato Growing Mistake #14: Pruning Your Tomato Plants Incorrectly

Pruning your tomato plants can have several advantages.

First of all, pruning off branches close to the ground can prevent disease.  The reason is that water from rain or irrigation cannot splash disease-carrying soil onto these lower leaves if they are gone.

pruning shears
Pruning your tomato plants prevents them from getting overgrown, and makes it easier to see and harvest the fruit.

Second of all, pruning tomato plants will yield fewer but larger fruits with better quality, and it will make the plants easier to manage.  As mentioned above, they will also be less likely to fall victim to diseases.

Finally, topping off (pruning) indeterminate tomato plants that grow too tall will prevent them from falling over. For more information, check out my article on tall tomato plants & pruning.

For more information, check out this article on pruning tomatoes from the University of New Hampshire Extension.

Common Tomato Growing Mistake #15: Using Containers That Are Too Small For Your Tomatoes

This applies to tomato plants grown completely indoors and also to seedlings started indoors to be transplanted outside.

If you use a container that is too small for a tomato plant, the plant will become root-bound.  This means that the roots go around in circle inside the container, looking for additional nutrients.

clay pots
Make sure to use containers that are large enough to support your tomato plants as they grow.

If this happens, you can transplant the tomato plant to a larger container with new potting soil that has plenty of nutrients for growth.


Now you have a much better idea of some of the common mistakes that gardeners make when growing tomatoes.  You also know how to avoid these mistakes, and what to do instead.

If your tomato plant has black on the stems or leaves, check out this article to learn more about why it might be happening.

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

If you want to read some of my most popular posts, check out the “Best of GreenUpSide” page here.  Enjoy!


Jon M

Hi, I'm Jon. Let's solve your gardening problems, spend more time growing, and get the best harvest every year!

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