Leaves on potato plant turning yellow?

Yellow potato leaves usually mean root or weather stress, but spots, twisted new growth, or sudden one-sided damage can point to disease or spray injury.

Answer what you can see

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Push a finger two inches into the soil. What does it feel like?

Which leaves are affected?

What has the weather been doing?

How fast did this happen?

These cannot always be told apart by the four answers alone: waterlogged roots and early blight after rain, low nitrogen and early blight on lower leaves, and drought or heat damage and herbicide or fertilizer burn after sudden yellowing; use the soil feel, leaf spots, twisting, and recent spray history to separate them.

The causes in full

Dry soil and heat stressMOST COMMON

How to tell
Check whether the soil is dry two inches down, leaves wilt in the afternoon, edges look crisp, or the yellowing is worst on the hot afternoon-sun side.

What to do
If the soil is dry and crumbly or baked hard two inches down, water slowly at the base until the root zone is wet, then mulch after the water soaks in. During scorching afternoons, use temporary shade cloth on the sun-facing side if practical, but keep potatoes in full sun overall.

Waterlogged soil and stressed rootsCOMMON

How to tell
Check for soil that stays wet two inches down, puddling after rain, a sour smell, and yellow lower leaves while the plant looks limp even though the bed is wet.

What to do
If the soil is waterlogged two inches down, stop irrigating until the top few inches are only damp and open shallow drainage channels so rain can run away from the row. Pull heavy mulch back temporarily and avoid fertilizing until new growth looks normal.

Low nitrogen or normal older-leaf agingCOMMON

How to tell
Look for steady yellowing that starts on the oldest, lowest leaves with no brown spots, no twisting, and otherwise normal new growth.

What to do
If the soil is not waterlogged and the oldest leaves are yellowing first without spots, side-dress with compost or a balanced vegetable fertilizer, keeping it off the stems and leaves. Water it in only if the soil is dry two inches down; otherwise let rain or normal irrigation carry it in.

Early blight fungal diseaseCOMMON

How to tell
Check yellowing leaves for brown spots, often with ring-like circles or yellow halos, starting low on the plant and spreading upward after wet weather.

What to do
Remove the worst spotted leaves, keep infected leaves out of the bed, and mulch so soil does not splash onto the foliage. When irrigation is needed because the soil is dry two inches down, water at soil level early in the day, and consider a labeled vegetable fungicide if spots keep spreading.

Late frost or cold-snap injuryLESS COMMON

How to tell
Check whether the yellowing appeared right after a cold night and is worst on tender tips, exposed leaves, or the side that thawed quickly in sun.

What to do
If the damage followed a cold snap or late frost, wait several days, then trim only tissue that turns brown and limp. Do not fertilize to force recovery; water only if the soil is dry two inches down.

Herbicide drift or fertilizer/spray burnLESS COMMON

How to tell
Check for a recent lawn weed killer, nearby spraying, fertilizer granules on leaves, or new growth that is twisted, cupped, pale, or yellowed more on one exposed side.

What to do
If spray or fertilizer damage is likely, do not add more fertilizer or spray; remove visible granules, and rinse leaves only if the spill is fresh and the soil is not waterlogged. If fertilizer was spilled and the soil is dry two inches down, irrigate once to dilute salts; if herbicide drift is the cause, there is no quick cure, so protect the plant from further drift and watch for healthy new growth.

Will it recover?

Yellowed or scorched potato leaves usually do not turn green again, so the goal is healthy new growth while removing only leaves that are dead or clearly diseased.

Stopping it happening again

Grow potatoes in full sun in loose, well-drained soil, keep moisture steady during dry spells, mulch after the soil warms, avoid overhead watering when disease is present, rotate where potatoes grow each year, and protect rows from spray drift.