Chilli pepper: lower leaves turning yellow

What it is likely to be on chilli pepper

1. Magnesium deficiency

   Candidate 1common on this plant

   ·source

   Sourced guidancemoderate confidence

   • Royal Horticultural Society: Magnesium deficiency
   • Penn State Extension — Pennsylvania State University: Pepper nutrient disorders

   Checked 2026-08-13

   Yellowing between the veins of the OLDER, lower leaves while the veins themselves stay green. Magnesium is mobile within the plant, so it is withdrawn from old growth to supply new — which is exactly why the pattern starts at the bottom.

   Points towards it

   • · magnesium sits at the centre of the chlorophyll molecule, and when it is withdrawn the tissue between the veins goes first while the veins keep theirs
   • · magnesium is mobile, so the plant strips it out of the oldest leaves to keep the fruit and the growing point supplied
   • · it usually appears a few weeks into a high-potassium tomato feed, which competes with magnesium at the root
   • · container and growbag culture under glass is where it is commonest

   Argues against it

   • · an evenly yellow leaf with the veins fading too is nitrogen or ageing — magnesium always spares the veins — this rules it out entirely.
   • · a mobile nutrient cannot run short in new leaves while old ones stay green; that pattern belongs to iron — this rules it out entirely.

   Check this next

   Pick a yellow leaf and hold it up against the sky. Magnesium leaves a sharp green skeleton of veins on a yellow background, and on peppers and aubergines it climbs the plant from the bottom while the fruit sets — the timing against the feeding is the confirmation, because it appears weeks after a high-potassium tomato feed was started rather than at the beginning of the season.

   What to do now

   Water in Epsom salts at about 20g per litre, or spray the same solution onto the foliage on a dull day for a faster response, and ease off the high-potassium feed for a fortnight. This is safe if the diagnosis is wrong — the worst case is a little wasted magnesium sulphate — which is why it is worth doing before anything more drastic.

   ·source

   Sourced guidancemoderate confidence

   • Royal Horticultural Society: Magnesium deficiency — treatment

   Checked 2026-08-13

2. Normal leaf ageing

   May be normalcommon on this plant

   ·source

   Sourced guidancemoderate confidence

   • Royal Horticultural Society: Chillies — cultivation

   Checked 2026-08-13

   Not a problem, and included as a candidate because it is one of the commonest explanations for a single yellow leaf on an otherwise healthy plant. Every plant sheds its oldest leaves; a differential that cannot return 'nothing is wrong' will always find something to blame.

   Points towards it

   • · a chilli carrying a heavy crop withdraws what it can from its lowest and most shaded leaves and puts it into the fruit
   • · it is limited to the bottom of the plant, under the canopy, where little light reaches
   • · nothing was done to it, and the plant is cropping normally

   Argues against it

   • · yellowing that reaches the growing tip is not the plant funding its fruit — it has run short of something — this rules it out entirely.
   • · a marbled green-vein pattern is magnesium being withdrawn, which is worth correcting

   Check this next

   Count the fruit before you diagnose the leaves. A chilli in August with a full set of pods and yellowing leaves at the very bottom of the plant, under the shade of everything above them, is spending its reserves exactly where it should — the check is whether the growing tips are still dark green and setting new flowers, in which case there is nothing to correct.

   What to do now

   Pick the yellow leaves off to improve airflow around the base and keep feeding as normal while the plant is fruiting. If you would rather have more leaves than more chillies, the lever is picking pods earlier rather than adding fertiliser — a plant with fewer fruit to fill holds its lower leaves longer.

   ·source

   Sourced guidancemoderate confidence

   • Royal Horticultural Society: Chillies — cultivation

   Checked 2026-08-13

Narrow it down

This page lists everything at once, which is the right shape for reading and the wrong shape for deciding. The interactive tool asks one question at a time, starting with whichever would separate these causes fastest, and stops as soon as further answers would not help.

Opens with the plant and the symptom already set. Nothing you answer is stored or sent anywhere — the answers live in the address bar and nowhere else.

What this does not cover

These are the causes GrowingHQ holds rules for on chilli pepper — not every cause there is. Where several problems look alike, the honest answer is often that they cannot be told apart by eye, and a page that named one would be guessing. If none of the above fits, the general lower leaves turning yellow page lists causes across all plants, and the Chilli pepper profile lists the problems it is prone to.