11 Tomato-Growing Mistakes You Should Avoid This Year

From leggy seedlings to collapsed trellises, we’ve all had our fair share of mishaps with tomatoes. In this article, former organic farmer Logan Hailey shares science-backed tips to avoid common tomato mistakes and improve your yields.

In the brown soil, a small tomato seedling emerges, showcasing its tender, pale green stem reaching for the sunlight. Its delicate leaves, with serrated edges, unfurl gracefully, poised to photosynthesize and nurture the growing plant.

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Juicy homegrown vine-ripened tomatoes are the keystone of the summer garden, but these vigorous plants aren’t always easy to grow. Leggy starts, improper spacing, fallen over trellises, or lack of flowers are just a few disasters that can fall on your tomato patch.  Armed with key insights on the mistakes to avoid, you’ll grow healthy plants with a higher yield.

Tomatoes are very forgiving but still demand a few basic growing conditions to produce the scrumptious heirlooms or ultra-sweet cherries we crave. If you’ve ever had tomato plants that turned yellow, flopped over, or failed to produce fruits, you know how frustrating it can be.

As a production-scale organic farmer, I have made most of these mistakes at one time or another (and the stakes were much higher considering that the tomatoes were part of our livelihood). Luckily, every mistake is an opportunity to learn. Tomatoes readily bounce back! I want to help you avoid these common pitfalls so your hard work doesn’t go to waste. 

1. Seeding Too Soon

Nestled within the brown soil, amidst a layer of brown mulch, tomato seeds rest on the surface. A gentle hand meticulously distributes these tiny seeds, each one a potential future tomato plant. Their small, oval forms promise the future bounty of juicy red fruits.
Within a mere week of germination, tomato seedlings can double their size.

Tomatoes are best seeded indoors 5-7 weeks before your expected last frost date. If you start the seeds too soon, the seedlings may become leggy and weak. “Leggy” means the stems are elongated and floppy rather than stout and strong. 

Legginess can happen due to insufficient sunlight, overly close spacing, or just staying in a container for too long. The latter is the main issue caused by seeding too early. A healthy and robust start to life is essential for a resilient, high-yielding tomato plant later in the season.

Tomatoes are super vigorous plants that quickly outgrow their pepper cousins in the greenhouse. A tomato seedling can double in size in just a week after germination. If your tomatoes are seeded too early in the spring, they will rapidly outgrow their containers.

When it’s warm enough to transplant outdoors, they could be completely rootbound or even flowering. Premature flowering in a pot is bad because the plant will undergo excessive shock during transplanting. 

Why You Don’t Want Tomato Seedlings to Flower Too Early

Within the dark soil, a youthful tomato plant thrives. Its supple, green stems display a resilient upward growth, while the leaves, vibrant and verdant, spread outwards like an emerald canopy, capturing the essence of growth and vitality.
To successfully transplant tomatoes, avoid seeding them too soon.

Tomatoes have two main phases: the vegetative phase (where they grow leaves, shoots, and roots) and the reproductive phase (where they produce flowers and fruits). If you seed too early and the plants sit in a pot for too long, they may get tricked into flowering too soon. Think of it like a teen pregnancy. That plant is still very young and growing. It isn’t a good time for reproduction!

The shift into reproductive growth means the seedling will funnel energy into flowers and fruits rather than roots and shoots. If you plant that seedling in your garden, it may become stunted and take longer to recover from transplant shock. It will have to shift back into vegetative growth to produce a strong root zone and luscious leaves to fuel tomato production later in the seasons.

However, if you are growing tomatoes in a container and have already planted them in a large enough pot (at least 5 gallons) with sufficient soil, it is fine to let them flower early as long as there are plenty of leaves. The main problem arises when the plant is still in a cell tray or 4-inch pot far too small to support adult growth. If you want to transplant tomatoes successfully, don’t seed them too soon! 

What to Do Instead

Housed in small, azure pots filled with rich brown soil, young tomato seedlings showcase their leaves, showcasing their tender, light green leaves, an emblem of early growth. These pots hold the promise of future harvests, nurturing potential red jewels.
Ensure that the seedlings you pick are not rootbound, leggy, or in the flowering stage.

Don’t get too excited in the spring! Wait until 5-6 weeks before your last frost date to sow tomatoes indoors. If you accidentally seeded too soon, all is not lost! You can up-pot your plants to larger containers to help them hold out until the weather warms out in your garden. 

Remember that tomatoes can form roots all along their stems. If you have leggy seedlings in 4-inch pots, you can remove a few lower sets of leaves and plant the seedling extra deep in a 1-gallon container of soil. Remove any flowers and provide plenty of water to see if the seedling can bounce back before transplanting outside in 1-2 weeks.

Alternatively, you can purchase nursery-grown tomato seedlings around the same week as the last frost date. When choosing your seedlings, ensure they are not rootbound, leggy, or flowering. A happy tomato seedling should have: 

  • Many sets of true leaves
  • Vibrant green foliage
  • A strong and thick stem (at least thicker than a Sharpie marker)
  • Roots that have filled out the container (but are not winding around in the shape of the pot)
  • Absolutely NO flowers or fruits

Seeding too soon won’t destroy your tomato crop, but practicing patience and recording your seeding dates each year is best. I like to keep a garden log to remember what worked best in seasons prior. If your first round of tomatoes was scrappy, no worries! Compost them and start again. 

You can always practice succession planting (growing multiple rounds of a crop) by sowing tomato seeds every 1-2 weeks for the first month of spring. This is great for staggering the harvest of determinate tomatoes (like canning or paste varieties) for multiple canning opportunities in the late summer and fall.

2. Insufficient Spacing

In a capacious, ebony tray, bathed in the richness of dark soil, numerous tomato seedlings sprout with vigor. Their youthful stems, slender and straight, gracefully extend upwards, while their leaves, an expanse of lush green, speak of life's resilience and abundance.
When plants are given enough space, they yield better results.

One plant with sufficient spacing is always going to yield better than several plants crammed together! Nobody can thrive when they’re squished together like sardines on a Subway train. In fact, most people get quite upset and sick when in overly crowded quarters. Similarly, garden crops planted too close together tend to get very stressed.

Insufficient spacing causes susceptibility to many problems, including:

  • Disease: Plant diseases like powdery mildew and blight spread quickly between closely spaced plants because there isn’t enough airflow between the leaves.
  • Leggy Growth: Just like a forest with lots of spindly trees growing super close together, plants have trouble reaching enough sunlight when they are all bunched together. The stems may become spindly, long, and weak rather than stout and strong. 
  • Resource Competition: There is only so much soil, water, sunlight, and nutrients in a given garden space. Densely spaced plants (or crops overgrown by weeds) have trouble getting the resources they need because they compete with their neighbors.
  • Low Yields: Research shows that the number of tomato fruits declines with closer spacing. Wider spacing almost always yields more fruit because the plant has more resources and less competition.

Thinning Seedlings

Within diminutive, obsidian pots, cradling brown soil, small tomato seedlings thrive. Their young leaves, a testament to their tender beginnings, flaunt a vibrant shade of green, promising the joys of homegrown tomatoes in the making.
When thinning, use your fingernails or fine needle-nose pruners to remove weaker seedlings carefully.

The nursery is often the first place beginners make this mistake. They eagerly sow dozens of tomato seeds in a small pot or cell, and the seeds germinate in a big clump.

Having so many baby plants may seem exciting, but they will quickly become sick if you don’t thin them. There is no problem with sowing extra seeds (I often do 2-3 per cell) to account for any germination issues, but thinning is crucial for early plant success.

Thinning your seedlings means choosing the strongest seedling in each cell or pot to keep. Yes, you need to choose just one! Multiple seedlings per pot can only cause more problems down the line. Use your fingernails or fine needle nose pruners to snip away the weaklings. Cut the unwanted seedlings at the base rather than pulling them. Pulling them could disrupt the root zone of the single seedling you want to thrive.

Proper Transplant Spacing 

A man adorned in white gloves gently transplants a tomato plant into the brown soil. Surrounding them are other transplanted tomato companions, sharing the earth's embrace. A small shovel stands sentinel in the soil, a symbol of nurturing care.
Planting tomatoes too closely together reduces vitality and ensures fewer resources are available per plant.

The next major mistake happens during transplanting. It may seem logical to put as many plants in one bed as possible, but this will actually reduce your overall yields. If you plant your tomatoes too close together, they will all have reduced vigor and fewer resources.  An 8-10” tall tomato seedling can look pretty small in the garden, but you must remember that it will grow into a massive bush or vine (depending on the variety). 

Tomato fruit production exponentially declines with closer spacing. But yields increase with wider spacing! The exact recommended spacing depends on the tomato variety and your trellising systems, but here are some general rules of thumb:

  • Space rows 4-6 feet apart (or staggered plants in a raised bed)
  • Space determinants 12-24” apart (wider in humid climates)
  • Space indeterminates 24-36” (closer if you plan to prune and trellis upward)

If you don’t plant in rows or use raised beds, imagine every tomato with its own “personal space” bubble instead. If the listed spacing is 24”, the plant needs 24” in every direction from the base of the stem to the base of the adjacent plant. You can also imagine a 2-foot square around each plant. In square-foot gardening, tomatoes usually do best with 2 squares per plant. Staggering in a zigzag pattern can help you maximize space in a raised bed setting.

What to Do Instead

In the brown soil, potted tomato plants reside snugly within plastic, ebony pots. Their leaves, lush and vibrant, are ready for the imminent transplant. The plants are meticulously spaced to maximize growth and vitality.
To reduce spacing, you can employ trellises like lines or fence stakes.

Give your plants space to breathe from day one. Remember, it’s not about how many plants you can fit in one space but how much fruit you can yield from a single happy plant. I would rather have two vigorous plants loaded with tomatoes than five spindly plants with only a few fruits per vine. The standard 24” spacing is a great place to start.

Feel free to experiment with spacing based on your tomato varieties, trellises, and bed sizes. But when in doubt, go wider than you think! Wider spacing is always better than cramped close spacing.

You can certainly grow tomatoes in a small-space garden, but you should choose dwarf varieties and prune them to a single or double leader (more on this below). Trellising them upward on lines or fence stakes can help reduce spacing. 

3. Improper Trellising

 A display of thriving tomato plants reveals a tapestry of orange and green fruits dangling amidst verdant leaves. These plants stand tall, supported by a trellis, a testament to nature's ability to bear fruit when nurtured with care.
Choosing the wrong trellis system can lead to numerous issues.

Tomatoes need adequate support to thrive. Allowing a tomato to vine along the ground without a trellis is a big mistake for many reasons:

  • The fruit gets dirty and rots in the soil
  • Slugs, caterpillars, and pests feast on the plant
  • The foliage usually turns yellow and becomes damaged
  • The plant cannot reach its fullest yield potential
  • Reduced air circulation causes disease

However, the wrong trellis system can cause just as many problems! Modern tomatoes have been bred to yield abundant amounts of heavy, juicy fruits. The branches can get weighed down without proper support, particularly if you are growing a beefsteak or heirloom variety. A collapsed plant can even snap its main stalk, rendering it a failure for the season.

Determinate vs. Indeterminate Supports

A close-up of plump tomato fruits. Their hues range from vibrant orange to deep green, nestled among a profusion of lush leaves and sturdy branches, a symphony of colors and life in a garden's embrace.
Indeterminate tomatoes, unlike their bushy counterparts, struggle to provide self-support.

Determinate (bush variety) tomatoes may naturally grow stout but are still susceptible to falling over if they’re not supported. After all, these are not trees! They may grow a central stalk, but it’s usually not strong enough to support the whole plant like a trunk. 

However, determinates have a “determined” window of time for production. They produce all their fruits in one big flush, which is great for canning and preservation. In the garden, this growth cycle means they won’t need continued support for the entire season. The best trellis systems for determinates are easy to install and remove, like tomato cages, ladders, and weaves (explained below).

Indeterminate (vining) tomatoes are even more unprepared to support themselves than their bushy relatives. The wild nightshade ancestors of tomatoes (Solanum pimpinellifolium) had far tinier fruits and a weedy, ground-creeping habit. We don’t want our indeterminates to creep on the ground, but we also don’t want them to collapse once they’ve climbed 6 feet in the air with 15 pounds of fruit dangling from the branches.

Because modern cultivars have been bred to produce much larger fruits, they need more robust support. Indeterminates do best with strong, tall trellises and regular pruning to encourage greater fruits and upright growth. They will continue growing and fruiting until the frost, so they need a really sturdy trellis to support them throughout the entire season. Avoid the mistake of plopping a wimpy plastic tomato cage over an indeterminate! 

What to Do Instead

A healthy tomato plant with lush green branches and vibrant leaves is thriving, supported by a sturdy trellis structure. The branches extend gracefully, showcasing the promise of future fruit.
To ensure your tomatoes thrive, always have a trellising plan before planting.

To keep your tomatoes upright and happy, never plant without a trellising plan in place! You should always set up your trellis before transplanting. This will save you a lot of headaches and prevent your trellis from disrupting any roots already in the ground.

The best tomato trellising systems include:

  • Tomato Cage: This classic trellis is the easiest option for a home gardener or container gardener. These cylindrical cages are typically made from galvanized steel for maximum longevity and support. It’s best to avoid the plastic ones. The cage keeps the plants upright and allows branches to splay out the sides, providing resting support for heavy fruit clusters. You can secure the stems to the cage with twist ties or twine if needed. Place the cage over your tomato immediately after transplanting. It is very difficult to wrangle a tomato cage over an established large plant. 
  • Stake Method: Wooden or metal stakes can greatly support individual plants, but you must tie the main stems or vines to the stake as they grow. A T-post fencing support is a strong and durable choice. Drive the stake in the ground before transplanting.
  • Basket “Florida” Weave: This method is commonly used in commercial tomato farming, but it’s great for home gardeners growing a long row of 5 or more plants. Create a structure of stakes at 3-5 foot intervals along the row, then weave twine or string horizontally between the stakes. The twine holds the tomato branches in, creating a central woven row. Basket-weave every 1-2 weeks as the plants grow to keep them upright and supported.
  • Fence Trellis: If you have a cattle panel, chicken wire, or plastic mesh fencing, you can create this simple trellis for a vertical tomato garden. I prefer to anchor the sides of a fence trellis with T-posts, then attach the mesh using strong wire. Keep a fence trellis on the northern side of the garden so the wall of tomato growth doesn’t shade out your lower-growing plants.
  • Archway Trellis: For a beautiful tomato walkway, bend a cattle panel between two beds as an archway tunnel. Both sides of the arch must be thoroughly supported by metal or wooden posts. Alternatively, grow your tomatoes along a decorative pergola! 
  • A-Frame Twine Method: An A-frame can be purchased or created with wooden 2x4s leaned against each other and one central beam across the top. Suspend strong twine or hemp rope from the center beam and train your tomatoes to grow upward in a single-leader pruning system.

If you don’t stake or trellis your tomatoes, you may suffer a disappointing harvest and face many disease problems. Save yourself the trouble and avoid this mistake by investing in a simple trellising system that you can reuse every year.

4. Choosing the Wrong Variety

A cluster of multiple tomato plants boasts a striking display of red, orange, and green tomato fruits hanging from their robust vines. The leaves, dark green and speckled, provide a verdant backdrop to this vibrant harvest.
Avoid randomly picking a tomato variety from your seed catalog or local nursery unless you feel experimental.

Selecting the right tomato seeds is essential for a successful harvest. Don’t just haphazardly choose a tomato variety from your seed catalog or local nursery without researching it first. 

If you choose a long-season tomato and your summer is extremely short, you may have disappointing yields and subpar fruits. A sauce tomato may be wildly disappointing if you’re craving juicy BLTs and Caprese salads. Different tomatoes are bred for specific growing conditions and culinary purposes. 

What to Do Instead

A close-up of ripe, orange-red tomato fruits hanging in abundance from the leafy branches. The leaves, with their waxy texture and deep green hue, encircle the fruit clusters like a protective canopy.
Growing tomatoes requires effort, so choose your varieties wisely to get exactly what you want.

Tomatoes take a lot of effort to grow, so be sure to plan ahead which varieties are worth your time and money. The two most important considerations are:

  • Days to maturity (based on the length of your season)
  • Culinary use (slicers, cherries, heirlooms, or sauce tomatoes)

Choosing Variety Based on Season Length

A close-up reveals a unique tomato variety with squash-like fruits in shades of vibrant orange and pale green. The leaves, dark and slightly serrated, contrast beautifully with the unusual fruit shape and colors.
Consider the length of your growing season before selecting tomato seeds.

Before picking your tomato seeds, consider the length of your growing season. Most tomatoes require 60-100 days to mature. The plants usually bear fruit 2 to 3 weeks after the first flowers appear. Indeterminates (vining types) will continue to bear fruit all season long, while determinants (bush types) will produce all their fruit in one big flush.

Here are a few points explaining the vast diversity in tomato maturity rates:

  • Large fruited varieties like ‘Beefsteak’ can take up to 100 days to ripen.
  • Cherry tomatoes generally take 60 to 70 days to produce their first fruits.
  • Varieties like ‘Sub Arctic’ ripen in as little as 45 days, perfect for short-season growers.
  • Some tomatoes like ‘Early Girl’ can yield in very early spring if they are started indoors and transplanted out with protection.
  • Sauce and canning tomatoes like ‘Roma’ yield in one big flush within 70-80 days.

Use the National Gardening Association’s frost-date calculator to find estimated first and last frost dates for your area. Then, calculate the amount of frost-free days you have. 

For example, many parts of the Northeastern U.S. are in zone 5, with an estimated frost-free season between May 15th and October 15th. This is only 153 days without frost! It wouldn’t make sense to direct seed a ‘Beefsteak’ tomato in late May because it takes up to 85 days for the plant to ripen its first fruit. You would only have less than a month of production!

Moreover, autumn comes quickly in the north, and the shorter days with less heat could cause an abundance of green fruits that are reluctant to ripen.

To enjoy the maximum harvest window, try to grow varieties that mature within a reasonable window of time based on your weather. Southern zones don’t need to worry as much about the frost-free window but should instead prioritize:

  • Varieties labeled for heat-tolerance
  • Regional adaptation to the south
  • Drought-tolerance
  • Direct seeding, if desired

Short-season northern growers should opt for:

  • Varieties labeled “early” and “quick maturing”
  • Cold-tolerant varieties like ‘Glacier’
  • Cherry tomatoes that mature in 50-65 days
  • Season extension like a greenhouse, tunnel, or row cover
  • Heirlooms specifically adapted to northern regions
  • Starting seedlings indoors whenever possible 

Culinary Use

 A close-up features clusters of red-orange, circular tomato fruits hanging in abundance from a branch. In the blurred background, other tomato plants hint at a bountiful garden filled with these delicious gems.
Numerous tomato varieties exist, each possessing distinct characteristics.

Choose your variety based on what you enjoy eating! There are hundreds of different types of tomatoes, but they aren’t all suited for interchangeable uses. For example:

  • Determinate (bush) sauce tomatoes yield dense, low-water-content fruits all at once, but they may not taste as good when sliced fresh 
  • Cherry tomatoes produce super sweet clusters all season long, great for fresh eating
  • Heirloom tomatoes are often juicy and flavorful, ideal for salads
  • Slicer hybrids are dense and less watery, great for sandwiches and burgers

If you’re unsure what variety to pick, here is a great place to start:

Not all tomatoes are created equal! You can always plant several varieties to find what tastes best for you. Find a balance between maturity times, flavor, texture, and growth habits! Don’t forget to label your plants and match your trellis selection with each variety you grow.

5. Inadequate Sunlight

In a rich and dark soil bed, tender tomato seedlings emerge, their young leaves reaching skyward with a vibrant green hue. These promising saplings hold the potential for a fruitful future.
The absence of flowers is often due to a lack of sunlight.

One of the worst mistakes you can make is planting your tomatoes in a partially shaded area. The plants will grow leggy and weak, can become very pale in color, and may experience stunted growth. If they do produce flowers and fruit, the yields will be reduced due to a lack of photosynthetic capacity.

Lack of sunlight is a common reason for the absence of flowers. If your plants only seem to grow pale green foliage, they are probably too shaded to produce fruits.

What to Do Instead

A close-up showcases shiny and small tomato fruits, their vivid orange hues catching the sunlight. The leaves, glossy and dark green, provide a lush backdrop to the glistening gems of the garden.
In your garden, ensure that your tomatoes occupy the sunniest location available.

These sun-loving plants demand at least 6-8 hours of direct sunlight every day. You should give your tomatoes the sunniest spot in your garden. Avoid anywhere that buildings, trees, or large shrubs cast a shadow. The only exception to this rule is in extremely hot climates. Tomatoes can benefit from some afternoon shade if your summers tend to have scorching sunlight and triple-degree temperatures.

A south-facing bed is the ideal location for tomatoes, but you must remember that the sun moves its pattern of light in different seasons, latitudes, and hours of the day. It’s helpful to use an app like SunCalc to check the sun’s position over your yard at any given time.

Sunlight not only impacts the lush growth of the leaves, but it’s also vital for improving your yields. Plants grown in shade will have noticeably fewer fruits or none at all. Tomatoes are day-neutral, which means they flower regardless of day length. However, they flower earlier and more abundantly when the days are long and they receive a lot of sunlight. 

6. Excessive Nitrogen Fertilizer

A gardener wearing protective gloves carefully holds a small shovel filled with white nitrogen fertilizer. With a gentle and precise touch, the fertilizer is spread across the brown soil, nourishing the young tomato plants awaiting its embrace.
Massive leafy plants without any fruit can result from high soil nitrate levels.

This heavy-feeding crop needs lots of nutrients to fuel abundant leaf and fruit production. However, you can also give tomatoes too much of a good thing. Dumping on the nitrogen fertilizer is a common mistake that many beginner growers hope will boost their yields. Oftentimes, the opposite happens.

Excessive nitrogen causes an overgrowth of foliage at the expense of flowers and fruit. This is particularly problematic when you use a synthetic or quick-release fertilizer. High levels of nitrates in the soil lead to a burst in vegetative growth and can cause massive leafy plants without any fruit. Too much nitrogen can cause nitrogen toxicity that damages or kills the plant.

Key signs of excess nitrogen include: 

  • Overgrowth of vegetative structures (stems, runners, leaves)
  • Abnormally dark green leaves
  • Yellowed leaf tips
  • Leaf tips that turn downward
  • Thin, lanky, leggy stem growth
  • Absence of flowers
  • Absence of fruit

What to Do Instead

A hand presents dark, organic soil, rich in nutrients and teeming with life. The earthy texture hints at its fertility, promising a thriving environment for plant growth.
It’s advisable to opt for organic fertilizers as they release nutrients slowly.

Always use a balanced fertilizer on your tomatoes. Feed them at the time of planting and provide a small side-dressing when they start flowering. Balanced means the N-P-K (nitrogen, phosphorous, potassium) numbers on the front of the bag are close together. Organic fertilizers are best because they are slow-release and less likely to cause fertilizer burn. 

My personal favorite is Espoma Tomato Tone Organic Plant Food. This fertilizer is 3-4-6, meaning the potassium ratio is the highest, and the nitrogen is the lowest. Potassium is one of the most vital nutrients for tomatoes because it regulates fruiting. Other great sources of potassium include wood ash and quality compost.

If fertilizing with compost alone, try to avoid high-nitrogen manures like chicken manure. Again, a balanced blend of cattle manure, vegetable waste, and a nice carbon source like rotted leaves can help provide your plants with a slow-release, gentle supply of nutrients that keep them happy all summer. Plants need nitrogen, just not too much! After all, we are trying to grow tasty fruits, not leaves!

7. Overwatering

Nestled within the warm embrace of brown soil, young tomato plants stretch their tender stems and leaves. A watering can hovers overhead, generously dousing the earth, causing water to pool and shimmer around the base of the plants, nourishing their roots.
Excessive water makes tomato plant root systems vulnerable to root rot by saturating the soil.

Overwatering is a common mistake with gardeners, but it can be extra detrimental for tomatoes. When tomato plants are regularly overwatered, the soil gets waterlogged, and their root systems become prone to root rot

This serious condition compromises the plant’s ability to absorb nutrients and water, which ironically can lead to wilting. Some gardeners see a droopy plant and mistakenly dump more water on it. Tomatoes are undeniably thirsty crops, but you can give them too much of a good thing!

Common signs of overwatering include:

  • Droopy or wilted leaves 
  • Blossom end rot
  • Yellowing leaves
  • Soggy soil (when you stick your finger in it, it comes out like brownie batter)
  • Puddled water near the base
  • Downward curling leaves
  • Fungal diseases like powdery mildew or mold
  • Busted or cracked fruit

Here’s more on the 7 Signs You’re Overwatering Your Tomatoes.

What to Do Instead

In a column of brown soil, young tomato plants stand tall, their vibrant green leaves reaching for the sun. Drip irrigation lines snake beside them, ensuring their thirst is quenched.
To ensure proper tomato care, maintain consistent soil moisture levels.

Always check the soil before watering! If you stick your finger 4-6” into the soil and your skin comes out clean, the soil is probably too dry. If your skin comes out muddy, you are likely overwatering. The key to tomatoes is consistent moisture. Avoid large fluctuations (long dry periods followed by heavy watering), or you may face problems with root rot. 

Water tomatoes 1-3 times per week, depending on the weather and soil properties. Drip irrigation or soaker hoses are best, and well-drained soil generously amended with compost will help moderate the soil moisture level.

Heavy clay or compacted soils are the most prone to overwatering because there is reduced pore space between the soil particles. Avoid planting tomatoes in poorly drained soil and instead opt for raised beds with lots of organic matter.

You should also avoid overwatering just before your tomatoes ripen. Excessive water can dilute the sugar concentration of the fruits, leading to less flavorful tomatoes. Many professional growers cut back on water for several days before a big harvest. Thanks to their strong root systems, mature tomatoes often don’t need as much water during the later life stages. 

8. Underwatering

Within the dry, withered soil, feeble tomato plants cling to life, their leaves brown and brittle. Each plant leans on a sturdy wooden stick for support.
The most significant problem during the seedling stage is insufficient watering.

When tomatoes don’t get enough water, they become stressed and wilt, drop their flowers, or crack their fruit. Tomatoes have fairly deep root systems (up to 3 feet) but aren’t totally immune to drought. While they can handle longer periods without water than some other crops, you should still provide tomatoes with a consistent moisture supply. Drought-stricken soil or large fluctuations from dry to wet can cause many undesirable problems.

Underwatering is the biggest issue during the seedling stage. If you recently transplanted your tomatoes, you must monitor them every couple of days to ensure they are hydrated. Plants that experience water stress early in life won’t grow as quickly or produce as early as healthy, hydrated plants.

To make matters more confusing, underwatering and overwatering often have similar symptoms. The key differences you’ll notice in an underwatered plant include:

  • Wilting that looks dehydrated rather than droopy 
  • Dry, brittle leaves
  • Dropped flowers
  • Bitter tasting fruits
  • Tough fruit skins
  • Blossom end rot

This mistake is especially common in sandy soils that don’t hold onto water very well.

What to Do Instead

A man in white gloves carefully spreads straw mulch on the brown soil, nurturing a tomato plant with green fruits dangling from its branches. The leaves provide a lush backdrop to the promising bounty.
During scorching summer days, closely watch plants as they may need supplemental watering.

Just like overwatering, this issue is only remedied by regular inspection. Don’t be afraid to touch the soil! It is the only reliable way to know if your plants are hydrated or not. Most tomatoes can’t be watered on a defined schedule (i.e., once per week) because the weather and growth stage are always changing. 

Ultra-hot summer days are the most vital times to check on your crops. This is when you need to provide a deep watering (i.e., a long drink) to saturate the lower layers thoroughly. Frequent, shallow watering is not great for these plants because it encourages shallow roots, and the upper layers of soil dry out faster. Fortunately, there are several strategies for improving soil moisture-holding capacity so you don’t have to water as often.

Here are some easy tomato-watering tips:

  • Generously amend the soil with compost or peat moss to hold water longer.
  • Container plants need to be watered more often. When irrigating, pour water until it comes out of the bottom drainage hole.
  • Plant your tomatoes extra deep to enable them to root along the buried stem segment and increase their root density.
  • Mulch around the base of your plants with straw or dried leaves to retain moisture.
  • Consistency is the most important way to prevent blossom end rot and other issues.

9. Overhead Watering

A watering can showers life-giving water onto tomato plants, their green fruits glistening with droplets. The leaves sway with gratitude as they soak in the moisture.
Watering tomato plants from the top allows water droplets to linger on the leaves.

Water that directly hits the foliage and stems of tomato plants can cause major fungal issues. Early blight and late blight are common killers of tomatoes, and they thrive in wet conditions. It is a big mistake to water tomatoes with sprinklers because the water droplets sit on the leaves for long periods of time. 

The little droplets can also act as magnifying glasses, causing the sun’s UV rays to intensify and potentially burn or scorch the leaves. If the canopy is thick, sometimes the overhead irrigation will only soak the leaves and won’t reach the root zone where it needs to go. The compounding stress and leaf damage can lead to more problems with disease.

Overhead watering can also cause soil compaction because the heavy impact of sprinkler sprays displaces any exposed water droplets. This is why super rainy areas tend to have a lot of erosion. Of course, you can’t change the rain, but you can modify your irrigation system.

What to Do Instead

In a well-tended garden, tomato plants thrive with lush green leaves, while their fruits display a striking mix of green and orange hues. The soil stays nourished, thanks to the efficient drip irrigation system.
Consider spacing your plants further apart to promote better airflow and facilitate quicker drying.

Drip irrigation and soaker hoses are the best irrigation options because they deliver water directly to the base of your plants. This allows maximum infiltration and keeps the soil moist for longer. Better yet, it reduces weed pressure because you aren’t watering the entire bed surface. The water only reaches your desired crops.

If you must overhead water, do it in the morning so the foliage has plenty of time to dry off in the afternoon sun. You can also increase the spacing between plants to encourage maximum airflow and drying winds through the leaves.

10. Forgetting to Prune

Precision is employed as pruning shears delicately trim the tomato plant's branches. The remaining branches, adorned with lush leaves, continue to nurture the plant.
Neglecting to prune suckers in tomato plants can substantially decrease your yields.

A lack of pruning often leads to the same issue as excessive nitrogen: overgrowth of leaves at the expense of fruit. Tomatoes produce a lot of extra foliage and stems called “suckers.” These suckers are lateral branches that emerge from the central vine and try to grow into new vines.

They’re called “suckers” because they suck the energy away from fruit production, using a lot of plant resources to expand the vining foliage. Neglecting to prune your suckers can significantly reduce your yields.

Increased Disease Risk

A close-up reveals the vulnerability of tomato leaves, marred by brown spots and signs of blight. The once robust foliage now struggles against disease.
When all the leaves are visible, it becomes easier to detect pests and diseases.

Sure, an unpruned tomato plant will still produce fruits, but it won’t be nearly as productive or tidy. The overgrowth of an unpruned plant can welcome lots of pest and disease issues due to overcrowding and restricted airflow. This creates an overly humid environment in the plant canopy, welcoming in fungal diseases like early blight, late blight, and powdery mildew.

Additionally, the plants just look messy and out of control. Pruning keeps your garden tidy and healthy while ensuring abundant harvests. It makes it easier to train your vines up their trellis.

Pruning is crucial for tomato health because it improves air circulation in the plant canopy and reduces disease risks. It is much easier to discover pests and diseases when you can clearly see all the leaves. Harvest is also streamlined without so much thick foliage hiding your fruits. 

Energy Allocation

A hand meticulously trims the suckers sprouting from the tomato plant's branches. The green leaves surrounding these growths seem vibrant, eager to receive more sunlight.
Trimming suckers redirects energy away from excessive vegetative growth, facilitating this crucial shift.

Most importantly, pruning ensures proper energy allocation. A plant only has so much energy that it can produce through photosynthesis. But where is it focusing its sugary resources? Toward roots and shoots, or flowers and fruits? The former is great during the early vegetative stage after transplanting, but the latter is obviously vital for a big harvest. Snipping the suckers shifts the energy allocation away from excessive vegetative growth.

Each time you snip off a sucker, it tells your plant, “Stop growing new vines and put that energy toward the fruit.” Still, some varieties will persistently produce suckers all summer long because they are so vigorous. But pruning can make the plant prioritize fruit growth so you get larger and greater quantities of tomatoes. 

What to Do Instead

A close-up of a woman's hand pointing out the excessive shoot that grows on a tomato plant stem in a greenhouse. In the background, a white mesh is seen under soft sunlight.
Start weekly maintenance of your tomato vines 1-2 weeks after transplanting.

Within 1-2 weeks of transplanting, begin a weekly sweep of your tomato vines. Choose a single-leader or double-leader trellising system. This means you will select only one or two central vines and remove all the rest.

Use clean, sanitized pruners to cut off all lateral suckers. You can identify a sucker by looking for stems that emerge from the “elbow ditch” where a leaf intersects with the main stem. Always take suckers to the compost pile after pruning so they don’t welcome diseases as they rot on the ground near the base of your plants.

If you’re a bit intimidated by tomato pruning, this video will clear everything up:

11. Lack of Companion Planting

Tomato fruits adorn the branches, displaying a mesmerizing blend of orange and green. Lush foliage provides a verdant backdrop to their beauty.
Interspersing tomatoes with other companion plants encourages biodiversity and reduces pest pressures.

The final mistake many growers make is planting their tomatoes in isolation. A monoculture area of tomatoes seems like a good idea at first because you can streamline your maintenance and harvesting to one area of the garden.

However, this also creates a big beckoning sign to pests and diseases. The concentration of tomato smells draws in bugs from near and far to feast on the buffet of tomatoes without any interruption or deterrent from nearby plants.

What to Do Instead

A large, orange-fruited tomato plant shares its space with vibrant marigold blooms. The tomato leaves offer shelter to the marigold's cheerful yellow leaves, with a screen supporting their harmonious growth.
Blend beneficial plants into your tomato beds to improve ecological resilience.

Grow tomatoes in a diverse bed or plant beneficial species in nearby beds. Greater diversity leads to greater ecological resilience. This can confuse pests, reduce disease risks, and improve the overall health of your plants. Plus, flowers and herbs simply make your garden prettier.

Companion plants can help your tomatoes by:

  • Deterring pests with their strong smell
  • Attracting beneficial predatory insects that feed on pests
  • Attracting pollinators to improve fruit set
  • Adding harvests to the unused bed space at the base of your plants
  • Improving yields
  • Deterring soil-borne issues like root-knot nematodes

The best companion plants for tomatoes include:

  • Marigolds
  • Basil
  • Parsley
  • Borage
  • Calendula
  • White alyssum
  • Cilantro
  • Sunflowers

Always ensure your tomatoes have sufficient space between their foliage and the companions. I usually provide at least 12-18” of space between my crop and the companion. You don’t want a giant sunflower to shade out your tomatoes, but the flowers can still be beneficial if grown in an adjacent bordering bed. Similarly, a huge bushy basil plant could cause a lack of airflow in the lower part of a tomato, leading to mildew or stem rot issues. Airflow is always key!

If planting companion plants directly next to my tomatoes, I typically choose lower-growing species that can occupy the space under the tomato canopy. Stout French marigolds and low-growing white alyssum are nice for lining the corners of a raised tomato bed.

Final Thoughts

Proper timing, spacing, support, sunlight, and water yield happy tomatoes. Tomatoes are not as complicated to grow as they seem. If you avoid these simple mistakes, you can grow the most gorgeous, abundant, and delicious tomatoes you’ve ever tasted:

  • Don’t start your seeds too early, or you’ll have leggy starts. Aim for 6 weeks before the last frost.
  • Give tomatoes enough space and support. 12-24” for determinants and 24-36” for indeterminates.
  • Choose tomato varieties that suit your season length and culinary needs.
  • Ensure plants get 6-8 hours of direct sunlight.
  • Use a balanced organic fertilizer and avoid excessive nitrogen.
  • Water consistently to avoid overwatering and underwatering.
  • Water at the base of your plants to prevent foliar disease.
  • Prune your plants for better airflow and energy allocation to fruit production.
  • Experiment with companion plants to improve tomato health.
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