Tomato Plant Problems: Diagnose by Symptom
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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
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
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People also ask
Why are my tomato leaves turning yellow?
Best match: Nitrogen deficiency. Manageable if you act. Calculate yours →
Why are my tomato leaves curling?
Best match: Physiological leaf roll — usually harmless. Calculate yours →
What are the spots on my tomato leaves?
Can't reliably tell Early blight (Alternaria), Late blight (Phytophthora), and Septoria leaf spot apart from what you've described — they need different responses, so check the signs below before treating. Calculate yours →
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