Why is my kale turning yellow?

The 4 most likely causes

The cause of kale yellow leaves usually narrows to one of the items below, ranked by how often we see each in Growli's diagnostic chats. Work down the list — most readers find their answer in the top two.

1. Overwatering or poor drainage (Most likely)
   In most homes overwatering is more often a drainage problem than a frequency problem. Kale needs a pot with a drainage hole, a chunky free-draining mix, and a watering rhythm of about 1-1.5 inches of water per week, evenly. Soggy soil drowns the roots and the first symptom you see above ground is yellowing or wilting foliage.
2. Wrong light level (Likely)
   Kale tolerates lower light than most, but tolerating is not thriving. In dim conditions it slows down, drops older leaves, and becomes more vulnerable to overwatering because the soil never dries. Give it 6+ hours of sun, tolerates part shade.
3. Nutrient deficiency (nitrogen or iron) (Possible)
   If kale has not been repotted or fed in a year or more, the older leaves can yellow uniformly while the newest growth stays green — a classic sign of nitrogen depletion. Yellow leaves with green veins on new growth point to iron or manganese deficiency. A balanced liquid feed during the growing season usually resolves both.
4. Underwatering or letting it dry too long (Possible)
   Underwatering looks similar to overwatering at first — both produce limp, dull leaves — but the soil tells the truth. If the soil is dust-dry several centimetres down, water deeply. Kale prefers about 1-1.5 inches of water per week, evenly.

Why kale in particular

Kale is a hungry leafy crop that pulls a lot of nitrogen to build all that foliage, and nitrogen is mobile inside the plant, so when it runs short kale strips its oldest lower leaves first, fading them to a pale, even yellow while the growing centre stays green. Some bottom yellowing is simply age as you harvest up the stem. What isn't ordinary is a yellow wedge spreading inward from a leaf margin toward the midrib, a V-shaped chlorosis that signals black rot, a bacterial disease of brassicas.

Normal turnover, or real trouble?

The lowest, oldest leaves on kale naturally pale and yellow as the plant ages and as you strip them, so an even yellowing that climbs slowly from the bottom is ordinary; those leaves are simply spent, so pick them off. Read it as a problem when the yellowing shows on the newer upper leaves, when it spreads as a V pointing in from a leaf edge, or when whole plants go off-colour together.

How to diagnose in 60 seconds

Run these quick checks before you change anything — the right fix depends on what you find.

• Kale wants water about 1-1.5 inches of water per week, evenly. Push a finger into the mix and hold it against that: still damp well before it is due, alongside the symptom, is the overwatering signature.
• Are the yellowing leaves the oldest ones at the base, or the newest at the tips? Old-leaf yellowing is usually water or nitrogen; new-leaf yellowing is usually iron or root damage.
• Look at the back of a yellow leaf with strong light — any speckling, webbing, or sticky residue? That points to pests, not water.
• Tip kale out of its pot and look at the roots: firm and pale is healthy; brown, soft or sour-smelling is rot, which is the real cause behind most of these symptoms.

The fix — step by step

First read the pattern before acting. If only the old bottom leaves are fading on a hungry plant, strip them and give kale what it craves, a nitrogen-rich feed watered in around the base, plus a mulch to hold steady moisture, and growth greens up. But if the yellow forms a V driving in from the leaf margins with blackened veins, do not feed it; that is black rot, so pull and bin affected plants.

This is the recovery sequence Growli walks users through for kale with yellow leaves. Work through the steps in order; skipping ahead is the most common reason a plant fails to bounce back.

1. Stop watering and check the roots. Don't add more water yet. Unpot kale and look at the rootball — firm white roots mean you have time; brown mushy roots mean you need to act today.
2. Trim damaged roots and yellow leaves. Cut off any soft brown roots with clean scissors. Remove fully yellow leaves at the base — they won't green back up. Leave half-yellow leaves alone for now; the plant is still pulling nutrients out of them.
3. Repot into fresh dry mix. Repot into fresh, well-draining mix in a pot one size up. For kale, pick a spot with 6+ hours of sun, tolerates part shade.
4. Reset the watering rhythm. Water deeply once, then wait. For kale, that means about 1-1.5 inches of water per week, evenly. Use a finger or a moisture meter — never a calendar.
5. Resume feeding only after recovery. A stressed plant cannot use fertiliser and the salts will worsen the damage. Wait for at least one round of healthy new growth (4-6 weeks) before resuming a half-strength liquid feed during the growing season.

When this can't be saved

Most cases of kale yellow leaves are recoverable, but a few red flags point to a plant that has gone past the point of return. If you spot any of these, consider propagating a clean cutting and starting over.

• Every leaf has yellowed simultaneously and the stem feels soft at the base — root rot has likely consumed the plant.
• New leaves emerge yellow and crispy and never green up — the growing tip is damaged.
• The soil smells sour or sulphurous even after a thorough drying period.

Prevention

For kale, the single biggest preventative is matching its native rhythm: about 1-1.5 inches of water per week, evenly, 6+ hours of sun, tolerates part shade, and a free-draining pot with a working drainage hole. Group kale with plants of similar needs so you can water them as a batch rather than guessing per-pot. Set a calendar reminder to feed during the growing season but never feed a sick or freshly-repotted plant — wait for healthy new growth first.

Common questions

Related guides

• What's wrong with my plant? — the diagnosis apps compared
• Is kale toxic to cats and dogs? — mildly toxic to pets, per the ASPCA
• How often to water kale — the watering brief
• When to repot kale — pot size and timing
• Yellow leaves on plants — the full diagnostic guide across species
• What's wrong with my plant? — Growli's flagship diagnosis index
• Kale — curling leaves
• Kale — drooping
• Kale — brown spots
• Monstera — yellow leaves