Tomato Problems: Blossom End Rot, Splitting, Blight

The most common tomato problems — blossom end rot, fruit splitting, and early or late blight — usually trace to watering consistency and airflow rather than soil fertility or variety choice alone. Blossom end rot comes from a localized calcium shortage triggered by uneven watering, splitting comes from a sudden water surge after a dry spell, and blight is a fungal disease that spreads fastest in humid, poorly ventilated foliage. Distinguishing them by appearance is the first step to fixing the actual cause.

How do you tell these three problems apart?

Why does inconsistent watering cause blossom end rot if soil has enough calcium?

Calcium moves through a plant almost entirely dissolved in water moving up through the xylem, and it moves slowest to fruit, which transpires far less than leaves. When soil moisture swings between very dry and very wet, calcium delivery to developing fruit becomes erratic even if total soil calcium is adequate — the fruit simply doesn't get a steady enough supply during its critical early growth phase. This is why adding more calcium (crushed eggshells, lime) rarely fixes an existing outbreak; consistent watering does.

What actually prevents fruit splitting?

• Water on a consistent schedule — roughly 1-1.5 inches per week including rainfall, applied evenly rather than in occasional heavy soakings after long dry stretches.
• Mulch with 2-3 inches of straw or shredded leaves to buffer soil moisture swings between waterings and rain events.
• Harvest fruit that's already showing color a day or two before an expected heavy rain, since nearly ripe fruit is most prone to splitting from a sudden moisture surge.
• Choose crack-resistant varieties if splitting is a recurring problem in an area with unpredictable rainfall patterns.

How does airflow and spacing prevent fungal disease?

Fungal spores need moisture on leaf surfaces to germinate and spread, so anything that keeps foliage drier and better ventilated slows disease progression. Spacing tomato plants 24-36 inches apart rather than crowding them, pruning lower leaves that touch the soil, staking or caging plants upright instead of letting them sprawl, and watering at the soil line rather than overhead all reduce the humid, wet-leaf conditions that blight and other fungal diseases need to establish.

When is a tomato problem serious enough to remove the whole plant?

Blossom end rot and splitting affect individual fruit but not the plant's overall health — remove the damaged fruit and adjust watering, and subsequent fruit is often unaffected. Early blight, caught on a few lower leaves, can be managed by removing affected foliage and improving airflow without losing the plant. Late blight is the exception: because it spreads so fast and can jump to other plants and even overwinter in soil debris, a plant with confirmed late blight symptoms should be pulled, bagged, and disposed of (not composted) promptly.

Do container-grown tomatoes get these problems more often?

Yes, generally. Containers dry out faster than garden beds and swing between wet and dry more easily, which makes blossom end rot and splitting more common in container tomatoes than in-ground ones, even with attentive care. A self-watering container or drip irrigation on a timer reduces this risk substantially compared to hand-watering, since it removes the day-to-day inconsistency that's usually the actual trigger. Container size also matters — a 5-gallon pot dries out and swings in moisture far more than a 15-20 gallon one, so undersized containers see these problems more often.

Can fungicide actually stop blight once it's started?

For early blight, a copper-based or chlorothalonil fungicide applied at the first sign of spotting can slow spread on the remaining healthy foliage, though it won't reverse damage already present on affected leaves. For late blight, fungicide is far more effective as a preventive measure applied before symptoms appear during a stretch of cool, wet weather than as a treatment after infection is visible, since the pathogen spreads through tissue faster than most home treatments can keep up with. Removing infected material promptly remains the more reliable response for late blight regardless of fungicide use.