GrowingHQ

Cabbage: lower leaves turning yellow

2 causes GrowingHQ holds specifically for cabbage, what separates them, and what is safe to do before you are sure.

What you are looking at

The oldest leaves — those nearest the base — losing their green while the growing tip stays healthy. Extremely common on tomatoes and peppers, and one of the least specific signs in growing: at least four unrelated things produce it, and one of them is the plant behaving perfectly normally.

Described view

Two cabbage plants compared: one uniformly pale from the oldest leaves upward with the plant otherwise upright and the root system normal, and one lifted from the ground beside it with its roots swollen into the knobbled club-shaped galls of clubroot and the lower leaves yellowing and wilting in sunshine

What it is likely to be on cabbage

  1. Nitrogen deficiency

    Candidate 1common on this plant
    source

    Sourced guidancemoderate confidence

    • Royal Horticultural Society: Brassicas — cultivation
    • Agriculture and Horticulture Development Board — AHDB: Brassica nutrition

    Checked 2026-08-13

    The classic pattern is uniform yellowing that starts on the OLDEST leaves and works upward, because nitrogen is mobile within the plant and is withdrawn from old growth to feed new. That directionality is what separates it from most other causes of yellowing, and it is observable without any equipment.

    Points towards it

    • · nitrogen moves within the plant, so a short supply is taken out of the oldest leaves and put into the newest
    • · the whole leaf pales together, veins included, rather than marbling
    • · the entire plant is a paler green than it should be, not just the yellow leaves
    • · a bed crop on a long season is where this appears

    Argues against it

    • · a green vein network held against yellow tissue is magnesium rather than nitrogen, and feeding nitrogen will not touch it — this rules it out entirely.
    • · nitrogen shortage cannot show on new leaves while old ones stay green, because the plant robs the old to supply the new — this rules it out entirely.

    Check this next

    Stand back and judge the colour of the whole plant against a neighbouring one before looking at any single leaf. A brassica short of nitrogen is uniformly light green all over with the oldest outer leaves fading to yellow first, and it is SMALLER than it should be for the date — a full-sized plant with a couple of yellow bottom leaves is doing something else.

    What to do now

    Top-dress with a balanced general fertiliser or well-rotted manure and water it in, and expect the response in the new growth rather than in the leaves already yellow — those do not come back. Brassicas are on the ground for most of a year and a bed that fed them well in May is usually empty by August.

    source

    Sourced guidancemoderate confidence

    • Royal Horticultural Society: Feeding vegetables

    Checked 2026-08-13

  2. Clubroot

    Candidate 2occasional on this plant
    source

    Sourced guidancehigh confidence

    • Royal Horticultural Society: Clubroot
    • Agriculture and Horticulture Development Board — AHDB: Clubroot in brassicas

    Checked 2026-08-13

    A soil-borne organism that distorts brassica roots into swollen clubs, so the plant cannot take up water and wilts in sunshine while the soil is still wet. Its resting spores survive in soil for around twenty years, which makes it the one brassica problem that permanently changes what a plot can grow.

    Points towards it

    • · clubroot lives in patches of soil, so affected plants cluster in part of a bed while the rest of the row grows normally
    • · the organism needs wet soil to move, and is worst on heavy ground that lies damp
    • · a soil-borne problem of the bed

    Argues against it

    • · an entire crop paling evenly across a bed is nutrition, where clubroot takes some plants and spares their neighbours
    • · a vein pattern in the yellowing points at nutrient availability rather than at damaged roots

    Check this next

    Watch the plant at midday and then lift a bad one. A cabbage with clubroot wilts in the sun and recovers overnight WHILE THE SOIL IS STILL MOIST — the roots cannot supply the leaves — and when it comes up the roots are swollen into knobbly clubs instead of a fibrous system. Yellow lower leaves with normal white roots underneath are not clubroot, whatever else they are.

    What to do now

    Lift and bin affected plants with their root balls rather than composting them, and wash tools and boots before working elsewhere on the plot. The spores last around twenty years, so the practical response is raising future brassicas in large pots to a good size before planting, liming the ground towards pH 7, and improving the drainage — none of which cures the soil, all of which lets a crop outrun it.

    source

    Sourced guidancehigh confidence

    • Royal Horticultural Society: Clubroot — control

    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.

Work through it for your cabbage

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 cabbage — 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 Cabbage profile lists the problems it is prone to.