Why Are My Tomatoes Rotting on the Bottom? Causes, Fixes, and Prevention

You head out to check on your tomato plants, excited to see the fruits filling in — and then you spot it: a dark, sunken, leathery patch spreading across the bottom of an otherwise perfect tomato. It’s one of the most discouraging sights in the home garden, and it happens to growers across the United States every single season.

The good news is that tomatoes rotting on the bottom is almost always explainable, fixable, and — with a few adjustments — entirely preventable. This guide walks you through every likely cause, how to tell them apart, and exactly what to do next so the rest of your crop stays healthy.

What Does It Mean When Your Tomatoes Are Rotting on the Bottom?

When you see rot forming at the bottom of a tomato — the end opposite the stem — you are most likely looking at a condition called blossom end rot (BER). Blossom end rot is a disorder in which the tissue of the blossom end of the fruit breaks down and rots, reducing the quality of the fruit and the overall yield from the plant.

The tomato plant (Solanum lycopersicum) is particularly prone to this problem during active fruit development, and it can catch even experienced gardeners off guard. Blossom end rot is a common problem for tomato growers, causing dark, sunken spots on the bottom of developing fruit. It can appear when the fruit is still green or just starting to ripen and often surprises gardeners who think their plants are otherwise healthy.

The spot typically starts small and pale, then darkens rapidly. The first sign is a small, water-soaked patch — pale green to tan — at the very bottom of a green tomato, when the fruit is roughly half its full size. Over the following days, the spot expands and sinks inward, turning dark brown to black with a dry, leathery texture.

Pro Tip: Not all bottom rot looks the same. BER produces a dry, leathery black patch, while fungal or bacterial rot tends to be softer, wetter, and may show mold. Knowing the difference helps you treat the right problem.

Is Bottom Rot in Tomatoes Always a Sign of a Problem?

Not necessarily — at least not a serious one. Some blossom end rot is more or less normal in the first tomatoes of the season since the plants are usually under stress during the initial fruit set. Many gardeners panic when they see the first few affected fruits, not realizing the rest of the crop may come through just fine.

Tomato blossom end rot will usually affect the first round or two of fruits. Although blossom end rot can leave the plant vulnerable to disease, it isn’t a contagious condition, and it won’t travel among the fruits. So if only a handful of early tomatoes are affected, that alone is not cause for alarm.

That said, when rot appears on multiple fruits across multiple clusters, or when the damage is severe and widespread, it signals an underlying growing condition that needs attention. If the damaged portion of the fruit is small, you can trim it off and enjoy the rest of the fruit. For larger or more persistent rot, it is time to dig into the cause.

Watering Issues Causing Tomato Bottom Rot

Inconsistent watering is the single most common trigger for blossom end rot in US home gardens. Blossom end rot is a delivery problem, not a supply problem. Calcium moves through tomato plants exclusively via water, and when watering becomes erratic, delivery to the blossom end — the part farthest from the stem — collapses.

Blossom end rot is most common when the growing season starts out wet and then becomes dry when fruit is setting. A water-soaked spot at the blossom end of tomato fruits is the classic symptom of blossom end rot, and damage first appears when fruits are approximately half their full size.

Both overwatering and underwatering are problematic. The lack of calcium may be due to low calcium levels in the soil or — more often — soil that is over- or underwatered. Wide fluctuations in soil moisture reduce the plant’s ability to take up calcium from the soil. Container-grown tomatoes face this challenge more than in-ground plants. Blossom end rot tends to happen more often in plants grown in containers, as the soil is more susceptible to fluctuations in moisture.

Maintain a consistent supply of soil moisture. During the growing season, especially as the fruit is developing, tomatoes need at least 1 inch of water per week, supplied as rainfall or irrigation. Watering with a soaker hose is preferable to overhead irrigation in the home garden.

Pro Tip: Before watering, push your finger 2 inches into the soil near the plant. If it feels dry at that depth, water now. If it still feels moist, wait. This simple check beats any fixed watering calendar.

Light Conditions Behind Tomato Bottom Rot

Light itself does not directly cause blossom end rot, but it plays an indirect role through heat stress and sunscald — both of which can damage fruit and mimic or worsen rotting on the bottom and sides of tomatoes.

Fruits most subject to sunscald are those that have been exposed suddenly to the sun because of pruning, natural spreading of the plant caused by a heavy fruit load, or loss of foliage from diseases. Sunscald creates pale, papery, sunken patches that often appear on the side or bottom of the fruit and can be mistaken for BER.

Intense afternoon sun in hot US climates — particularly in the South and Southwest — accelerates soil moisture evaporation, making consistent watering harder to maintain. BER hits hardest on the first cluster of fruits each season, and again whenever development suddenly accelerates — after a stretch of cool weather breaks into heat, or when transplants push a flush of new growth. Providing shade cloth during peak afternoon heat (above 90°F) can reduce this stress significantly.

If you are growing tomatoes in a low-light area and compensating with extra fertilizer to boost growth, be cautious: rapid, lush growth driven by high nitrogen can actually worsen calcium delivery to the fruit. Steady, moderate light paired with consistent watering is the better combination. For more on how light affects plant health, see this guide on best houseplants for low-light areas — the same light-stress principles apply across many species.

Soil, Nutrients, and Root Health Causing Tomato Bottom Rot

Soil conditions are a major piece of the puzzle. Even when your garden soil contains adequate calcium, the plant may not be able to access it. Your calcium levels may be fine, but inconsistent watering, stress from heat or drought, or waterlogged soil may have prevented the plant from accessing it.

Soil pH matters too. Grow tomatoes in well-drained soil high in organic matter with a soil pH between 6.5 and 7.5. Outside that range, calcium becomes less available to roots even when it is present in the soil. A simple soil test — available through most US cooperative extension services — will tell you exactly where you stand before you add any amendments.

Fertilizer choices also affect calcium uptake. Too much nitrogen, or too much fresh manure in the soil, will prevent calcium uptake and will result in blossom end rot. Use fertilizers low in nitrogen, but high in superphosphate, with numbers similar to 4-12-4 or 5-20-5; this will reduce the chances of blossom-end rot.

Root damage is another underappreciated cause. Cultivating or digging around a tomato plant can damage their roots and prevent proper water and calcium uptake, which can lead to end rot. Be mindful to keep the roots intact and undisturbed. Rapid early growth of the plants can cause the rot because the calcium is needed by the tomatoes when they are actively growing and the plants may not be able to take up sufficient calcium quickly enough through the roots. It is important not to force the plants to grow too quickly to avoid this rot.

Soil Factor	How It Causes Bottom Rot	What to Do
Low calcium	Fruit tissue breaks down without enough calcium	Soil test first; add lime or gypsum if confirmed low
Wrong pH (below 6.2 or above 7.5)	Calcium becomes chemically unavailable	Amend soil to reach pH 6.5–7.5
Excess nitrogen	Blocks calcium uptake; drives lush leafy growth over fruit	Switch to low-nitrogen, phosphate-rich fertilizer
Root damage	Reduces water and calcium absorption	Avoid deep cultivation within 12 inches of stem
Waterlogged soil	Interferes with root nutrient uptake	Improve drainage; add organic matter

Environmental Stress Triggering Tomato Bottom Rot

Weather swings are a major driver of blossom end rot in US gardens. A cool, wet spring followed by a sudden heat wave — common in states like Texas, Georgia, and the Carolinas — creates exactly the kind of moisture fluctuation that disrupts calcium delivery.

Blossom end rot can be a physiological problem or can be caused by unfavorable conditions such as freezing or drought. In either case, the culprit is most often a lack of calcium, either in the soil or due to the plant’s inability to take it up.

High temperatures above 85°F increase the plant’s water demand faster than many gardeners adjust their irrigation schedule. A soaker hose laid at the base of your tomato row and covered with mulch delivers comparable results — run it for 20–30 minutes three to four times per week during dry spells, adjusting upward in heat above 85°F.

Mulching is one of the most effective environmental buffers available to home gardeners. Mulching tomatoes helps to conserve moisture in the soil. Use organic mulches such as straw free of weed seed, grass clippings, peat moss, or wood chips. A 2–3 inch layer of mulch around the base of each plant keeps soil temperature stable and dramatically reduces the moisture swings that lead to rot.

You can also consider companion planting with tomatoes to create a more stable microclimate around your plants — dense ground covers and companion herbs can help reduce soil temperature and moisture loss.

Pests and Disease Leading to Tomato Bottom Rot

While blossom end rot itself is not caused by a pest or pathogen, other problems can produce rot that looks similar — or that worsens existing BER damage. It is worth knowing the difference.

The lesion may become infected with black mold. This common tomato disease makes the fruit unpalatable and also affects its appearance. Secondary mold invasion is common once BER breaks down the fruit’s protective tissue, so what starts as a physiological disorder can look increasingly like a disease problem.

Southern blight is a genuine fungal disease that can cause rotting at or near the base of tomato plants and on fruit touching the soil. Southern blight is caused by the fungus Sclerotium rolfsii, which can infect a wide range of vegetable crops and herbs. White strands of fungal mycelium and small tan, round sclerotia resembling seeds may be found at the base of the stem. This disease is most common in warm, humid regions of the South and Southeast US.

Early blight, caused by the fungus Alternaria solani, primarily attacks foliage but can spread to fruit. Early blight can infect the fruit through the calyx or stem attachment in the immature green or red stage and can produce distinct target-like lesions similar to foliar infection. Defoliation caused by early blight can reduce fruit yield and can leave the fruit open to sunscald injury.

Blossom end rot is a physiological disorder of tomatoes and peppers — a disturbance in the normal physiology of the plant. Because it is not caused by an insect or disease organism, fungicidal and insecticidal sprays are not effective in controlling the problem. If you are seeing true BER, skip the fungicide and focus on watering and soil corrections instead.

Important Note: If you see white fuzzy mycelium at the base of the stem alongside wilting, suspect Southern blight rather than BER. Southern blight requires removal of affected plants and soil treatment — not a watering adjustment.

How to Diagnose Why Your Tomatoes Are Rotting on the Bottom

A quick, systematic look at your plants will usually point you to the right cause. Work through these observations before reaching for any treatment.

1. Look at the location of the rot. True BER appears only at the blossom end — the very bottom of the fruit, opposite the stem. Rot higher up on the fruit, near the stem, or on the sides suggests a different problem such as early blight or anthracnose.
2. Check the texture. BER rot is dry and leathery. The tissue underneath is brown and firm, not soft or mushy — unless secondary fungi have moved in, which turns it wet and black. Soft, wet rot with a foul smell points to a bacterial or fungal disease.
3. Note which fruits are affected. Typically, the problem starts during the first flush of fruits, and on those that haven’t quite reached their full size. If only early-season or first-cluster fruits show rot, BER is the likely culprit.
4. Review your watering history. Did you skip a few days? Did heavy rain follow a dry spell? Any significant moisture swing in the two weeks before rot appeared is a strong indicator of BER.
5. Check the soil. If you have not tested your soil recently, pick up an inexpensive test kit from a garden center or contact your local cooperative extension office. Inconsistent watering or a calcium deficit in your soil are the most common causes of end rot, but improper soil pH can also be a culprit as it influences the plant’s nutrient absorption.
6. Inspect the stem base. If you see white mold or small seed-like structures at the soil line, you may be dealing with Southern blight rather than BER.

Using a plant identification app on your iPhone or an Android plant ID app can also help you compare your symptoms against a database of known tomato diseases when you are unsure.

How to Fix a Tomato Plant That Is Rotting on the Bottom

Once you have confirmed blossom end rot, act in steps. The affected fruits will not recover, but you can stop new fruits from developing the same problem.

Step 1: Remove affected fruits. Damaged fruit will not recover; remove it to redirect energy into healthy growth. Removing fruit and leaves that have already started to rot will help the plant regain health faster.

Step 2: Stabilize your watering immediately. This is the single most effective intervention. Drip irrigation on a timer is the most effective tool for BER prevention because it removes the wet-dry cycling entirely. If you do not have drip irrigation, commit to a consistent hand-watering schedule and check soil moisture before every session.

Step 3: Address calcium if soil testing confirms a deficiency. If you do find your soil is truly lacking in calcium, you can add a bit of lime or gypsum to the soil or use a foliar spray to help the leaves take up calcium. According to Garden Design , sprays with calcium chloride or calcium nitrate can help new fruit but won’t fix existing damage. Apply according to label directions and combine with proper watering practices.

Step 4: Check and adjust fertilizer. If you have been using a high-nitrogen fertilizer, switch to one formulated for tomatoes with a lower first number on the label. An ordinary fertilizer contains nitrogen, potassium, and phosphorus, but these are not going to change the calcium levels. Instead, use a fertilizer for tomatoes that includes calcium.

Step 5: Be patient. Existing spots won’t heal, but new fruit can be symptom-free within two to three weeks if soil moisture and calcium levels are corrected.

Pro Tip: Skip the eggshell remedy as a quick fix. According to Garden Design , eggshells take months or longer to break down in soil. For calcium to reach your plants in time, it needs to be water-soluble — opt for garden lime or calcium nitrate instead.

How to Prevent Tomato Bottom Rot Going Forward

Prevention is far easier than treatment, and most of it comes down to building good habits before and during the growing season.

• Test your soil before planting. Test soil pH (target range 6.2 to 6.8) and calcium levels before planting. Apply lime or gypsum only if recommended by your soil test. Adding amendments blindly can throw off soil chemistry.
• Water deeply and consistently. Water deeply and consistently — 1 to 2 inches per week is typical. Mulch with straw, leaves, or compost to help retain moisture. Avoid letting soil dry out completely between waterings.
• Mulch generously. A 2–3 inch layer of organic mulch around each plant keeps moisture levels stable between waterings and is one of the cheapest, most effective preventive measures available.
• Avoid deep cultivation near plants. Avoid deep cultivation around the plants as much as possible after fruit set, especially in dry weather. Scraping the soil lightly with a hoe is usually sufficient to control weeds in the home garden.
• Choose resistant varieties. Heirloom varieties seem more prone to developing blossom end rot. Plum and pear-shaped tomatoes are also more susceptible. Some varieties that are resistant to BER include Mountain Fresh, Mountain Spring, and Mountain Delight.
• Use the right fertilizer. Avoid high-nitrogen fertilizers, especially early in the season. Choose a balanced fertilizer to encourage steady growth. When fertilizing, opt for nitrate-based nitrogen rather than ammonium forms, as ammonium can compete with calcium uptake and increase the chance of blossom end rot.
• Practice crop rotation. Rotating tomatoes to a different bed each season reduces the buildup of soil-borne pathogens like Sclerotium rolfsii that can cause secondary rot problems. Crop rotation with a non-susceptible grass crop, such as corn, is the most effective means of reducing numbers of sclerotia and resulting incidence of Southern blight.

You can also reduce stress on your plants by exploring what to grow alongside tomatoes — the right companions can improve soil health and reduce pest pressure season after season. If you want to expand your edible garden while managing plant health, browse the full range of plant types to find compatible additions to your growing space.

FAQ

Can I Still Eat a Tomato That Has Rot on the Bottom?

You can cut away the damaged area and eat the rest. Blossom end rot is a physiological disorder, not a pathogen, so the healthy flesh above the lesion is safe. If the rot is small, simply slice it off. If mold has moved in and the flesh smells off, discard the fruit.

Does Blossom End Rot Spread from Tomato to Tomato?

Blossom end rot is not contagious; each fruit develops symptoms on its own. Once conditions are corrected, future fruit will form normally. You do not need to worry about removing affected plants — just the damaged fruit.

Why Do My Container Tomatoes Get Bottom Rot More Often?

Plants growing in containers can be particularly susceptible to blossom end rot. This is because roots can become packed in tightly, which reduces the space for water. Growing in a larger container, watering more frequently, or using drip irrigation can all help prevent blossom end rot.

Will Adding Calcium Spray Fix the Problem?

Calcium sprays can help new developing fruits but will not reverse damage already done. According to The Old Farmer’s Almanac , inconsistent watering is the main cause of calcium deficiency. Avoid watering your plants too much or too little. Instead, water consistently and evenly. For most US gardeners, fixing the watering routine matters more than adding calcium.

Is Blossom End Rot the Same as a Fungal Disease?

Blossom end rot is a physiological disorder, not a disease. It happens when developing fruit doesn’t get enough calcium, usually because of uneven watering or other growing conditions. Because it isn’t caused by insects or fungi, fungicides and insecticides won’t help. Save the fungicide for confirmed fungal problems like early blight or Southern blight.

When Should I Worry That It Is Something Other Than BER?

If the rot is soft, wet, and spreading rapidly — or if you see white mold at the base of the stem — suspect a fungal disease rather than BER. Rapid wilting of the entire tomato plant alongside white mold covering the lower stem of tomato plants and the surrounding soil points to Southern blight, which requires a different response including plant removal and soil treatment. Contact your local cooperative extension service if you are unsure — they can confirm the diagnosis and recommend region-specific treatments.