10 Things You Should Never Do When Growing Tomatoes in Containers

You don’t need a huge garden to grow epic tomatoes. Containers and grow bags offer the perfect small-space solutions, but there are some things you should never do when growing tomatoes in pots. Garden expert Logan Hailey explains ten key mistakes to avoid in your tomato container garden.

Orange and green tomatoes dangle gracefully from the verdant vines, adorned with shimmering water droplets.

You don’t need a huge garden to harvest an abundance of tomatoes. Compact bush (determinate) varieties are perfect for growing in containers, pots, or grow bags. Proper sizing, soil, drainage, and maintenance are crucial for keeping these plants small and productive. 

However, there are some things you should never do when growing tomatoes in containers. If you avoid these ten container gardening mistakes, you’ll save yourself many headaches and enjoy epic tomato yields.

What are the Biggest Container Tomato Mistakes?

A potted tomato vine thrives, bearing ripe red and unripe green fruits, positioned elegantly against a backdrop of clean, white brick.
Tomatoes thrive in well-drained soil with consistent moisture levels.

Improper watering is one of the biggest mistakes that beginners make when growing tomatoes in containers. Potted plants need more water than their counterparts. Less soil volume in the container means that the soil dries out faster. However, the smaller space also means it is easy to overwater, causing soggy anaerobic conditions that can lead to root rot. 

A balance of drainage and consistency is crucial. Grow your tomatoes in large containers with drainage holes and quality compost-rich soil. Check the moisture level every other day in hot weather, and aim to keep the soil about the wetness of a wrung-out sponge. 

Other common mistakes with container-grown tomatoes include:

  • Planting in an undersized pot
  • Forgetting to prune
  • Failure to stake or trellis
  • Choosing the wrong varieties
  • Overfertilizing with nitrogen
  • Overcrowding several plants in one container

10 Things to Avoid with Container Tomatoes

Growing tomatoes in containers is very straightforward. Just like growing in raised beds or in the ground, your plants will need full sunlight, well-drained soil, balanced fertilizer, and consistent moisture. Proper spacing, container size, pruning, and trellising are also crucial for success. 

Tomatoes can grow quite large and yield in abundance, but they must have the proper conditions to thrive. Avoid these common mistakes for epic tomato yields from a container:

Insufficient Container Size

A tomato plant with ripe red fruits flourishes in a brown pot, its lush foliage suggesting robust growth.
Use large pots or fabric grow bags for optimal growth.

Successful potted tomatoes require the right-sized container. Tomatoes can grow roots two feet deep and wide or more! A small pot will not provide enough space for these plants to thrive. Moreover, a tiny pot can topple over from the weight of a heavily fruiting plant.

Grow your tomato plants in pots at least 10 gallons, ideally 15-20 gallons. This translates to an 18-24 inch diameter pot. When in doubt, choose the largest pot possible. Fabric pots are a great way to maximize space and soil volume while minimizing weight. Try a 15 gallon or larger grow bag, or opt for a small raised bed to grow several tomatoes in one place. 

Problems With Small Pots

Young tomato plants grow in black pots, soaking up sunlight for nourishment and growth.
Prevent rootbinding in potted plants by using large, porous containers.

A small pot also lacks sufficient soil volume to hold onto water during the hottest months. Tomatoes require plenty of moisture and are very prone to drying out while growing in containers. If you plant them in a small container, the soil may dry out quickly, and the roots can start winding around in circles. 

Rootbinding is a common problem with potted plants that leads to stunting and poor fruit production. Plants growing in small plastic pots are the most prone to rootbinding. Prevent rootbinding by growing in large, porous earthen or fabric pots that naturally “air prune” the roots. When the roots hit above-ground oxygen, they naturally stop growing.

Too Much Nitrogen

Tomato seedlings thrive in blue and gray planters; their green leaves soaking up the warm sunlight.
Organic fertilizers rely on soil microorganisms for slow-release nutrient availability.

We know tomato plants are heavy feeders, but there can be too much of a good thing. Overfertilizing with nitrogen is a common mistake. Excessive amounts of nitrogen cause tomato plants to produce a larger volume of leafy growth. This focus on foliar overgrowth detracts from fruit production. As the plant channels its energy into loads of leaves and stems, it may fail to produce flowers or fruit. 

The easiest way to avoid this mistake is to use a balanced, slow-release fertilizer. Balanced fertilizer means that the NPK ratios are close together. For example, 4-4-4 or 3-4-6. The latter is particularly advantageous because it has higher amounts of potassium and lower amounts of nitrogen. Tomatoes still need nitrogen, but they should not be overfed with it.

Slow-release means that the fertilizer gradually feeds the plant over time. Organic fertilizers are always slow-release because they require beneficial soil microorganisms to mineralize the ingredients. As the organic ingredients are transformed by microbes, they become available to plants. The result is long-lasting fertility that slowly becomes available to tomato roots throughout the season.

Avoid Synthetic Fertilizers 

White gloved hands cradle colorful fertilizer granules, while thriving tomato vines form a lush backdrop.
Overfertilization with synthetic products harms soil and waterways.

It’s best to avoid quick-release synthetic fertilizers because these products pose the most risk for overfertilizing. Quick-release nitrates add a mega dose of nitrogen to the soil all at once. These synthetic ingredients bypass the microbial “digestive system” of the soil. Instead, they funnel a big blast of nutrients to the roots. 

Home gardeners are particularly prone to overfertilizing with synthetic products. An excess of nitrates can also have detrimental effects on waterways, soil quality, and pest infestations. Because the plants receive a spike of fertilizer all at once, they require repeated applications that may imbalance the soil mineral profile and reduce overall yields.

Too Much Water

A green hose waters the soil around a potted tomato plant, nurturing its growth, with more plants visible in the background.
Excessive watering can suffocate potted tomato plants.

Proper irrigation is essential for all tomatoes, but especially for those growing in containers. Too much water can rapidly harm potted plant health because the water has nowhere to go. As a result, it accumulates in the bottom of the pot, creating conditions amenable to root rot, a major disease of tomatoes and many other plants. It is caused by a fungal pathogen that loves soggy, low-oxygen conditions. 

Potted tomatoes really dislike “wet feet.” If you imagine standing in a puddle all summer long, this is what an overwatered container plant feels like. The plant roots cannot properly breathe or function in waterlogged conditions.

Common symptoms of excess irrigation include:

  • Standing water at the base
  • Rotten, foul odor from the soil
  • Yellowing, blistered leaves
  • Mushy, soft leaves
  • A visible crust on the soil surface or lower tomato stem
  • Droopy, wilted foliage (in spite of wet soil)
  • Limp, mushy, black roots (healthy roots are whitish)
  • Cracked fruit

How to Prevent Overwatering

A vibrant yellow watering can sprinkles water over a thriving garden of lush tomato plants, nourishing their leaves and fruits with moisture.
Regularly check potted plants for soil moisture by using your finger.

First, ensure your container has adequate drainage. A large drainage hole at the bottom is ideal. Porous materials like terracotta and fabric pots are also useful for wicking away moisture. The tiny holes in the sides of those pots allow airflow to reach the root zone, which can prevent anaerobic conditions that lead to root rot. 

Next, prioritize checking your potted plants on a regular basis. A watering schedule (i.e. “water every other day”) is not ideal for container-grown tomatoes. Weather and conditions are always changing, so you cannot guarantee that the plant needs water every other day. Instead, use your finger to check the soil moisture. Make this a habit every time you walk by your plants. 

Here’s how to manually gauge soil moisture:

  • If you stick your finger several inches down and the soil feels like brownie batter, it is far too wet.
  • If it feels like a wrung-out sponge, the moisture is perfect, and you don’t need to water.
  • If it feels dusty or very little soil sticks to your skin, the plant needs water ASAP.

Lastly, check the drainage of your soil. Container plants tend to need even better drained soil than a raised bed or in-ground bed. This is because the soil is confined to a smaller space. Water should flow effortlessly through the soil profile. If you pour water onto the top of the soil, it should not puddle up. Puddling and slow drainage are signs that the plant needs to be repotted in a better mix.

Prioritize container soil mixes with:

  • Quality compost
  • Peat moss
  • Vermiculite
  • Perlite
  • Horticultural sand

Avoid adding clay-heavy garden soil into a container. If the plant is struggling with excess moisture, you can always repot it. Tomatoes are very amenable to transplanting as long as you are gentle and thorough. Use the transplanting process as an opportunity to check the roots for signs of rot. Prune away any brown, black, or mushy roots and sanitize your tools regularly.

Best Container Irrigation System

Ollas, traditional clay pots, rest on mulched soil, offering slow irrigation for plants.
Tomato roots regulate water intake based on soil moisture tension.

An olla (pronounced “oya”) is the best way to irrigate potted tomatoes. This ancient clay pot irrigation system is ideal for gardeners who tend to overwater. An olla is a porous terracotta pot that is buried in the potting soil near the plant’s roots. The olla is filled with water from the top and naturally releases moisture into the soil as needed. 

Thanks to an intriguing scientific phenomenon called soil moisture tension, the tomato roots only pull the amount of moisture they need. Once the soil is saturated, the olla stops releasing water through its porous earthen walls. All you need to do is bury the olla at the right depth and regularly check that it is full.

Too Little Water

A small tomato plant sits in a pot, thriving indoors under soft, filtered sunlight.
Fruit-bearing plants demand more water for continuous tomato production.

A lack of water can be just as problematic as too much water. If the soil is pulling away from the edge of your pot, it is likely too dry. Tomatoes are very thirsty crops, and container-grown plants are particularly vulnerable to drought stress. You may need to water your potted plant every day, every other day, or every three days, depending on the container size and the weather. 

The root zone of a container plant is limited by the volume of soil. There is no way for the roots to reach deeper in the ground, therefore you must ensure they have everything they need in a smaller space. Larger pots can go longer time frames without water. However, plants that are loaded with fruit naturally need more water to keep producing tomatoes.

Key symptoms of underwatering include:

  • Soil pulling away from the edge of container. This is usually the first sign.
  • Wilting
  • Dry, crispy leaves
  • Curled leaves
  • Yellow or brown foliage
  • Stunted, slow growth
  • Lack of flowers and fruit
  • Shriveled flowers or fruit

A lack of water is detrimental to tomato harvests and can dramatically reduce the yield, flavor, and texture of your fruits. After all, a tomato is about 95% water. Large-fruited varieties like beefsteaks are particularly in need of consistent moisture. 

But there is still something even worse than drought stress: huge fluctuations from dry to wet. If you go from drastic underwatering to dramatic overwatering, your tomatoes will be very unhealthy. The fluctuation from bone-dry to soggy soil is a major cause of blossom end rot, fruit cracking, and disease issues.

Shallow vs. Deep Watering

A yellow-green watering can pours water onto young tomato plants nestled in rectangular pots, nurturing their growth.
Inconsistent shallow watering leads to plant issues.

Overly frequent shallow watering is the main mistake that leads to drought stress. Frequent, shallow irrigation means giving the plant small amounts of water almost every day. This is not beneficial for root health or fruit production.  

Shallow watering only penetrates the upper few inches of soil. The bottom part of the container (where most of the roots are) remains dry and dehydrated. This inconsistent moisture can lead to major issues like low fruit production and blossom end rot.

In contrast, deep watering is ideal for tomatoes. This practice helps maintain consistent moisture so that there is always water available in the lower parts of the pot, even if the upper inches of soil dry out on a hot day. Remember, deeper soil is insulated against weather extremes because of its thermal mass and protection from the sun. The lower parts of the container act like a backup reservoir of water.

Whether growing in containers or beds, these plants prefer larger drinks of water at once. This means that you should irrigate less frequently but run the irrigation until water pours out of the bottom drainage hole. If there is no drainage hole in your pot, you may have to reach your arm in at the edge of the container to feel if the soil is moist at the bottom of the pot. 

Here is a quick reference chart to help you further understand the difference between these types of irrigation: 

Shallow Watering Deep Watering *Best for Tomatoes
Run the hose or irrigation lines for a few minutes Run the hose or irrigation lines for 30 minutes or up to 2 hours, depending on pot size and emitters
High frequency (watering every 1-2 days or multiple times per day) Less frequent (once every 2-4 days)
Water only soaks the upper few inches of soil (when you stick your hand in, the bottom feels dry) Water reaches deep into the lower 10-12” of soil
Roots become stunted and shallow Roots dig all the way to the bottom of the pot
Water puddles up on top or barely reaches into the soil profile Water runs out of the bottom drainage hole
Soil feels wet on the top and dry or powdery in the lower layers Soil moisture is like a wrung-out sponge throughout the pot

If you still feel confused about irrigating your potted tomatoes, try an olla. This clay pot irrigation (described in the previous section) is perfect for creating a balance between underwatering and overwatering.

Preventing Blossom End Rot

A thriving potted tomato plant bearing green fruits stands prominently, surrounded by fragrant herbs in the background.
Improper watering causes calcium uptake issues in tomatoes.

Have you noticed rotten, ugly “butts” on the bottoms of your tomatoes? Blossom end rot is commonly mistaken as a disease, but it is actually a physiological issue. It causes the flower-end of tomato fruits to turn brown, black, or mushy. The main cause of blossom end rot is a calcium deficiency. However, this doesn’t mean you have to dump on the eggshells, oyster shells, or other calcium fertilizers. 

Most garden soils (including potted soil blends) actually have plenty of calcium. The real problem is calcium availability. Improper watering is a top reason why your tomatoes are not able to uptake the calcium in the soil. The fluctuation from dry to wet is stressful for the plant, causing it to become mineral-deficient. Ironically, a similar response happens to humans when they become stressed. Stress is detrimental to our health, and it significantly harms your tomatoes, often causing them to rot while still on the vine!

Moral of the story? Keep the soil consistently moist. Try to avoid long periods of dryness, and water deeply but less frequently to keep those lower roots happy.

Containers Without Drainage Holes

A hand pours water from a white container onto the soil of a potted tomato plant, positioned on a white windowsill.
Fabric grow bags are made of permeable fabric that wicks away water.

It’s more difficult to water if your container doesn’t have adequate drainage. In regular garden beds, water can always flow deeper into the ground. But in a container, water must have some way to exit the bottom of the pot. It is a major mistake to plant tomatoes in pots without drainage holes. This can cause issues with root rot, overwatering, and stunted growth. 

Before you plant your tomato, check that there is at least one large hole at the bottom of the pot. So-called “self-watering” planters are not always the best because you cannot see the water pour out from the bottom. A standard pot-and-saucer makes it easier to irrigate. When the saucer fills with water, you know that you’ve properly irrigated the entire soil profile.

Grow bags are an exception to this rule. These fabric pots don’t have visible drainage holes, but they are made of permeable, breathable fabric. The fabric will naturally wick away water and help the roots breathe.

Growing in Low Light Areas

Colorful array of ripe tomatoes nestled in pots on a porch, featuring vibrant hues of orange, red, and deep purple.
Container gardening allows plants to be relocated for optimal sunlight exposure.

Container-grown tomatoes still need just as much light as their garden counterparts. Full sunlight is crucial for success! These plants are native to South America, where they’ve evolved for centuries under the hot, bright sun. A minimum of six to eight hours of direct sunlight per day is necessary for proper flower and fruit production. 

Key symptoms of insufficient light include:

  • Pale foliage
  • Wimpy, weak stems that easily topple over
  • Leggy or spindly stems (especially seedlings reaching up toward the light)
  • Long sections of stem between each set of leaves
  • Little to no flowers
  • Little to no fruit

The best thing about container growing is that your plants are mobile! A lack of sunlight is easily remedied by moving your tomato to a brighter location. Ensure the area is south-facing without any major shadows from buildings, shrubs, trees, or fences. 

If your tomato was growing in a very low-light area, make the adjustment easier by gradually introducing more light. Move it closer to the brighter sun every few days. Do not suddenly move a shaded plant into full sunlight, as this can cause leaf scorch and intense stress. The plant needs time to adapt.

Wrong Variety Selection

Lush tomato plants, reaching skyward in pots, display a vibrant mix of ripe red and green unripe fruits.
Look for compact tomato plants for better container gardening results.

Some tomatoes are just too big for containers. Unless you have a giant grow bag or raised bed, it is best to stick with compact varieties. In general, determinate (bush) tomatoes are the best for containers. These cultivars are bred to remain small and shrubby while still producing a lot of fruit at once. Of course, you can still grow indeterminate (pole) varieties as long as you provide a larger pot, trellis, and regular pruning.

The best tomato varieties for containers include:

  • ‘Supremo Roma’: A bushy sauce tomato with elongated, red fruits
  • ‘Tumbling Tom Yellow’: This compact, rambling cherry tomato is often grown in hanging baskets and window planters
  • ‘Glacier’: Determinate plants can grow with only a tomato cage
  • ‘Chocolate Cherry’: Flavorful purplish cherry tomatoes that easily grow on a trellis
  • ‘Better Bush’: Disease-resistant plants grow about 4 feet tall and remain compact

When searching for tomato seeds or seedlings, look for plants labeled as “compact” or “suitable for pots.” These plants naturally grow better in containers because they don’t require as much space. They often have shorter nodes between leaf sets and are bred to produce dense yields on smaller vines.

It is also important to match your variety selection with your culinary desires:

  • If you crave large sandwich-worthy slicers, look for heirloom and beefsteak types.
  • If you prefer sweet snacks, choose cherry types.
  • For canning, choose sauce varieties that yield low-moisture-content fruits in one big flush.

Lack of Trellis or Support

Healthy tomato plants bearing fruits, cradled within a potted environment, reinforced by wooden sticks to ensure sturdy growth.
Supporting plants with trellising maximizes space and fruit production.

Growing a potted tomato without a support can be a recipe for disaster. A wind storm can easily knock over your plants, especially if they are growing in smaller pots. Moreover, many varieties cannot support themselves once they are loaded with fruit. A simple tomato cage, T-post, or trellis system makes a huge difference in yields and maintenance. Lack of support is a common reason for messy container gardens and diseased plants.

Determinate tomatoes naturally have stouter, bushier growth. Still, most require a tomato cage to keep them contained. Indeterminate tomatoes have long, rambling vines that will quickly spill over a pot. You do not want fruits to develop on the soil, as this can predispose them to rot and pest damage. Instead, use a T-post, stake, or a taller tomato cage to train them upward.

Trellising is a great way to improve yields in a small-space container garden. By training the plants upward, you maximize vertical space without taking up extra ground area. More importantly, you can prune away side shoots (suckers) to help the plant focus on fruit production. Choose just one or two main stems where the plant can grow its fruit, then prune away the lateral shoots. This will create a tidy potted plant that is loaded with tomatoes. Removing excess suckers also ensures proper airflow to prevent disease.

Lack of Pruning

Fingers delicately poised, ready to pluck off a tomato plant sucker, aiding in growth.
Tomato plant suckers divert energy from fruit production.

Speaking of pruning, pro container gardeners should prioritize removing suckers from their tomatoes. After all, you want to make the most of a small space. If you neglect pruning, the tomatoes may overgrow a ton of foliage and fail to produce as much fruit as you desire. A lack of pruning can also lead to overcrowding.

Suckers are the side shoots that grow in the “elbow ditches” of tomatoes, right where a leaf stem intersects with the main stem. Indeterminate varieties produce more suckers than determinates. They are called suckers because they “suck” energy away from fruit production. Each sucker can grow an entirely new vine that is the same size as the plant. If you snip off the little suckers, it sends a message to the plant to focus on growing flowers and fruits.

Always use clean, sanitized shears. Remove prunings from the garden to prevent disease.

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Overcrowded Plants

Silver cans hang from a white porch railing, each bearing lush tomato plants.
Overcrowding leads to decreased yield and increased disease risk.

You should never overcrowd container-grown tomatoes! It is highly recommended to only grow one plant per pot. If you wish to grow multiple tomato plants in the same container, a small raised bed is a better option. This is because tomato plants need at least 24-36 inches of space in every direction in order to grow to their fullest potential. 

Overcrowded plants must compete for water, nutrients, and light. Too much competition is bad in any space, but especially in a small pot with limited resources. Nobody wants to be crammed like sardines in a subway, and your plants don’t want to be crammed into a small pot together. One well-cared-for plant in a large pot will typically out-yield a pot of two or three overcrowded plants. 

Lack of spacing also leads to a lack of airflow, which creates conditions for disease. Powdery mildew and blight spread rapidly between overcrowded tomatoes. If leaves are brushing up against each other in a jungle of growth, they are probably too close together. It helps to space your pots 8-12 inches apart to give each plant sufficient space to breathe.

Final Thoughts

The basic steps for successful tomatoes apply to container-grown plants, but you must pay more attention to spacing, water, and airflow.

Remember:

  • Never grow tomatoes in tiny pots.
  • Pay special attention to soil moisture. Pots dry out more quickly.
  • Ensure proper drainage. Overwatering causes soggy conditions that are amenable to root rot.
  • Choose compact varieties and properly support them with a cage or trellis.
  • Avoid overcrowding.
  • Prune to promote more fruit production in a small space.
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