Tomato Plant Problems: Diagnose by Symptom
Set your conditions — the recommendation updates instantly.
GardenSays
Most likely: Nitrogen deficiency. It's manageable if you act.
- Most likely
- Nitrogen deficiency
- Severity
- Minor
- Causes checked
- 5
Based on leaves turning yellow on the lower leaves with moist soil, the best match is nitrogen deficiency. Confirm it: Uniform pale-then-yellow starting at the bottom and creeping up; no spots; slow growth.
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.).
Why
- ✓A symptom tree ranks causes by how well your conditions match each cause's classic pattern — the distinguishing signs are how you confirm.
- ✓Most leaf problems trace to water, weather, or the two big 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 late blight or wilt until proven otherwise — photograph it and check with your county extension.
- →Multiple symptoms at once usually means the top cause here plus plain stress — fix watering first, then re-diagnose.
How this was calculated
- 1. Symptom
tomato: leaves turning yellow — 5 known causes evaluated
- 2. Your conditions
Location on plant: lower; soil: moist. Causes matching these conditions rank higher.
- 3. 1. Nitrogen deficiencybest match (score 8)
Distinguishing signs: Uniform pale-then-yellow starting at the bottom and creeping up; no spots; slow growth.
- 4. 2. Normal lower-leaf senescencescore 7
Distinguishing signs: Only the lowest, oldest leaves; plant otherwise vigorous and setting fruit.
- 5. 3. Overwatering / poor drainagescore 5
Distinguishing signs: Yellowing with a wilted, heavy look despite wet soil; may affect whole plant.
- 6. 4. Fusarium wiltscore 5
Distinguishing signs: Yellowing on ONE side of the plant or one branch first; wilting despite moist soil.
- 7. 5. Early blight (Alternaria)score 4
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)
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