Tomato Leaves Turning Yellow: What It Means and What to Do

Set your conditions — the recommendation updates instantly.

PlantWhat do you see?Where on the plant?Soil right now

GardenSays

Best match: Nitrogen deficiency. Manageable if you act.

Best match: Nitrogen deficiency
Severity: Minor
Causes checked: 5

Based on leaves turning yellow on the lower leaves with moist soil, the closest match is nitrogen deficiency. Confirm it against the actual plant: Uniform pale-then-yellow starting at the bottom and creeping up; no spots; slow growth.

This is a symptom-pattern match from your written description, not a lab diagnosis. If the plant is collapsing over days (not weeks), treat it as the worst plausible cause until ruled out.

Do this this week

1.Confirm it first: Uniform pale-then-yellow starting at the bottom and creeping up; no spots; slow growth.
2.Light nitrogen sidedress and water it in; expect visible greening within a week.
3.Collapsing fast (days, not weeks)? Photograph it and check with your county extension before treating

Calculated result · 3 verified sources · Checked 2026-07-15 · How we decide

The link reopens this exact calculation.

Why

What to do: Light nitrogen sidedress and water it in; expect visible greening within a week.

If that doesn't match what you see, work down the list: Normal lower-leaf senescence (only the lowest, oldest leaves; plant otherwise vigorous and setting fruit.); Overwatering / poor drainage (yellowing with a wilted, heavy look despite wet soil; may affect whole plant.).

A symptom tree ranks causes by how well your conditions match each cause's known pattern — the distinguishing signs are how you confirm it on the actual plant, not a lab result.
Most leaf problems trace to water, weather, or common leaf-spot fungi; true plant-killers are rarer but worth ruling out first.

When this doesn't apply

If the plant is collapsing fast (days, not weeks), treat it as the most severe possibility on the list until proven otherwise.
Multiple symptoms at once usually means the top cause here plus plain stress — fix watering first, then re-check.

How this was calculated

1. SymptomSource guidance
Tomato: leaves turning yellow — 5 known causes evaluated (extension-sourced)
2. Your conditionsCalculated result
Location on plant: lower; soil: moist. Causes whose known pattern matches these conditions rank higher — this narrows the list, it doesn't identify anything.
3. 1. Nitrogen deficiencymatch score 8Calculated result
Distinguishing signs: Uniform pale-then-yellow starting at the bottom and creeping up; no spots; slow growth.
4. 2. Normal lower-leaf senescencematch score 7Calculated result
Distinguishing signs: Only the lowest, oldest leaves; plant otherwise vigorous and setting fruit.
5. 3. Overwatering / poor drainagematch score 5Calculated result
Distinguishing signs: Yellowing with a wilted, heavy look despite wet soil; may affect whole plant.
6. 4. Fusarium wiltmatch score 5Calculated result
Distinguishing signs: Yellowing on ONE side of the plant or one branch first; wilting despite moist soil.
7. 5. Early blight (Alternaria)match score 4Calculated result
Distinguishing signs: Yellow areas around brown spots with target-like concentric rings, moving up the plant.

Data sources

University of Minnesota Extension — Growing tomatoes in home gardens (common problems) (checked 2026-07-15)
UMN Extension — What's wrong with my plant? (tomato diagnostic) (checked 2026-07-15)
Cornell Vegetables — Disease factsheets (checked 2026-07-15)

What changes this answer

Where on the plant?

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