Why are my pepper plant leaves turning yellow?
Peppers yellow their lower leaves most often from cold stress or nitrogen deficiency — they're extremely sensitive to cool soil and temperatures below 55°F at night.
Peppers are the most cold-sensitive common garden vegetable. Soil below 60°F slows root function dramatically; nights below 55°F cause yellowing and leaf drop even when air temperatures are above that threshold during the day. A pepper plant that went in the ground too early, or experienced a cold snap, will often shed a quarter of its older leaves before settling in. If nights have been cool and the yellowing is confined to older, lower leaves, warming temperatures tend to stop the problem on their own.
Nitrogen deficiency produces a different pattern — uniform pale yellow-green across older leaves, starting at the bottom and moving upward. The leaves don't spot; they just fade. This can happen in light or sandy soil without much organic matter, or in container plants that have exhausted the potting mix's nutrients. A side-dressing of balanced fertilizer or compost worked into the top inch of soil can improve color within 2–3 weeks.
Magnesium deficiency causes interveinal chlorosis — leaves turn yellow between the veins while the veins stay green. This is common in acidic soils and in heavy-fruiting plants. A foliar spray of Epsom salts (1 tablespoon per gallon of water) can improve this relatively quickly, though addressing the underlying soil pH is the longer-term fix.
Overwatering creates the same yellow-lower-leaf look by excluding oxygen from the root zone. If your bed or container stays wet for more than 3–4 days between waterings, reduce frequency before adding fertilizer — additional nutrients won't help if the roots are already compromised.
- AphidSoft, clustered insects on new growth causing curled leaves and sticky honeydew.
- Bird DamageBerries pecked or missing, seeds scratched from beds, and seedlings dislodged — birds feeding on ripe fruit, seeds, or soil grubs.
- Blossom DropFlowers fall before setting fruit, often during temperature extremes or after weather stress.
- Blossom End RotDark, sunken, leathery patch on the blossom end of tomato or pepper fruit — a calcium deficiency disorder.
- Cabbage MaggotBrassica transplants wilting and dying as white maggots tunnel through roots at or below the soil line.
- Why do my transplants look stunted and aren't growing?Cold soil, root-bound roots, or fertilizer burn can all stall a transplant — check soil temperature first before diagnosing anything else.
- Can you give a plant too much nitrogen, and what does it look like?Yes — excess nitrogen produces very dark green, lush leafy growth at the expense of flowers and fruit, and in high concentrations can burn roots and cause wilting.
- My soil pH is too high (alkaline) — what can I do about it?Sulfur is the standard amendment for lowering soil pH, but it works slowly — expect 6–12 months for meaningful change, and retest before planting rather than adding more based on symptoms alone.