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Harvesting & Storing

What Potato Plants Look Like When Ready to Harvest

Flowers mean new potatoes; yellowing, collapsing foliage means maincrop. How to read the plant above ground, and the two-week wait that makes them store.

By Salma 3 min read Save to Pinterest — opens Pinterest in a new tab
Freshly dug new potatoes still crusted with soil, beside a trowel on a garden path
Photo: Ruth and Dave, CC BY 2.0, via Flickr
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Potatoes grow where you cannot see them, so the plant above ground is the only instrument you have. Fortunately it is a clear one — once you know whether you are growing new potatoes or maincrop, because the two want opposite-looking plants.

Reading the plant

What the foliage is telling you
Plant looks likeStageWhat to do
Lush, green, no flowersTubers still formingWait
Green and floweringTubers bulkingNew potatoes ready — dig if you want them
Lower leaves yellowingMaturingGetting close; stop watering
Most foliage yellow, stems floppingSenescingNearly there
Foliage brown and collapsedMatureWait 2 weeks, then lift

Die-back looks alarming the first time. A healthy potato plant collapsing into a brown heap is not a disease — it is the crop finishing. The plant is emptying itself into the tubers.

Unless it collapsed suddenly and smells

Blight also kills potato foliage, but differently: dark water-soaked patches spreading fast in cool wet weather, often with a distinctive smell, and it can take a plant down in days while still green elsewhere. If that is what you are seeing, cut the haulm off at ground level immediately and wait three weeks before lifting, so spores on the surface do not follow the tubers into storage.

New potatoes are a different question

New potatoes are simply immature tubers, harvested deliberately early for thin skins and sweetness.

Dig them while the plant is green and healthy, around the time it flowers — roughly 60–90 days after planting depending on variety.

They will not store. Thin skins are the point, and thin skins mean days, not months. Eat them within a week.

Checking without committing

Bandicooting — scrape soil away from the side of the mound with your hand, feel for tubers, judge the size, then push the soil back. The plant carries on unbothered and you know what you have.

For a whole row, lift one plant at the end as a test dig. Whatever that plant shows, the rest are doing roughly the same.

The two weeks that decide whether they keep

This is the step that gets skipped, and it is the one that matters for storage.

After the foliage has died back, leave the tubers in the ground for about two weeks. During that time the skins set: they go from rubbing off under a thumb to firm and tight. Set skins are the difference between potatoes that keep for months and potatoes that rot in a few weeks.

Test it with your thumb. If the skin still scuffs easily, give it longer.

Lift sooner if the ground is waterlogged, slugs are working, or a hard frost is coming — then cure them under cover instead.

Lifting and curing

Choose a dry day. Loosen with a fork well outside the plant — start a foot away, because a fork through a potato is a potato that will not store.

Do not wash them. Brush off loose soil once dry; soil is protective and water starts rot.

Cure in a single layer somewhere dark, airy, and 50–60°F for about two weeks. This thickens skins further and heals harvest nicks.

Store at 40–50°F in the dark, in paper sacks, hessian or an open crate — never sealed plastic. Check monthly and remove anything soft.

Green potatoes are not salvageable by peeling

Any tuber exposed to light turns green and produces solanine, which cooking does not destroy. Cut green parts away generously, and discard anything thoroughly green or bitter. This is why storage must be genuinely dark, not just shaded.

Common questions

What does a potato plant look like when it is ready to harvest?

For maincrop potatoes, the whole plant tells you: the leaves yellow from the bottom up, the stems weaken and flop, and the foliage collapses and browns. That die-back is the plant moving its last reserves into the tubers. For new potatoes it is different — harvest while the plant is still green and healthy, around the time it flowers, since you are taking immature tubers deliberately.

Do potatoes have to flower before you harvest them?

No. Flowering roughly coincides with tubers beginning to bulk up, which is why it is a useful signal for new potatoes, but some varieties flower sparsely or not at all and still crop perfectly well. Judge maincrop by the foliage dying back, not by whether flowers appeared.

How long after the plants die back should you dig potatoes?

Wait about two weeks after the foliage has died down before lifting maincrop potatoes. That period lets the skins set — they go from rubbing off under a thumb to firm and tight, which is exactly what determines whether they store for months or rot in weeks. If the weather is wet or slugs are bad, lift sooner and cure them under cover instead.

How do you know if potatoes are big enough without digging up the plant?

Scrape a little soil away from the edge of the mound with your hand and feel for tubers, then push the soil back. This is called bandicooting and it tells you the size without sacrificing the plant. You can also lift one whole plant from the end of a row as a test dig, which is the surest way to judge the rest.

Can you leave potatoes in the ground too long?

Yes. Tubers left in wet soil after the foliage dies are exposed to slugs, wireworm and rot, and in warm soil they may start to sprout. In areas with hard frosts, leaving them risks freezing damage. Two weeks after die-back is the sweet spot — long enough to set skins, short enough to avoid the losses.

How do you cure potatoes for storage?

Lay unwashed potatoes in a single layer somewhere dark, airy and around 50 to 60F for about two weeks. Curing thickens the skin and heals small harvest wounds. Then store in the dark at 40 to 50F in paper or hessian, never sealed plastic. Do not wash them before storing — soil protects them, and moisture starts rot.

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