When to Harvest Maincrop Potatoes

Knowing when to harvest maincrop potatoes is essential for achieving good yields, thick skins, and long storage life. Unlike early potatoes, maincrop varieties are grown to full maturity and need correct timing to avoid rot, damage, or poor keeping quality.

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What Are Maincrop Potatoes?

Maincrop potatoes are slower-growing varieties planted in spring and harvested later in the season. They produce larger tubers with thicker skins and are best suited to long-term storage through autumn and winter.

When Are Maincrop Potatoes Ready to Harvest?

Maincrop potatoes are usually ready 18–20 weeks after planting.

Typical UK timing:

• Planted: April
• Harvested: September to October

The key signal is when the foliage turns yellow and dies back naturally. This indicates the plant has finished growing and tubers have reached full size.

Why Foliage Dieback Matters

Once the foliage dies back:

• Tuber growth has stopped
• Skins begin to thicken and toughen
• Potatoes become suitable for storage

Harvesting before dieback results in thin skins that damage easily and store poorly.

Should You Cut Back Foliage Before Harvesting?

In some cases, foliage is cut back 10–14 days before harvesting. This is often done if:

• Blight has appeared
• You want to encourage skin set
• Growth is still lush late in the season

Cutting foliage allows skins to harden, improving storage quality.

How Long Can Maincrop Potatoes Stay in the Ground?

Maincrop potatoes can stay in the ground for up to 3–4 weeks after foliage has died back, as long as conditions are dry and mild.

They should be lifted before:

• Prolonged wet weather
• Heavy frosts
• Soil becomes waterlogged

Leaving them too long increases the risk of rot, slug damage, and frost injury.

How to Check If Maincrop Potatoes Are Ready

You can check readiness by:

• Digging up one plant to inspect tuber size
• Rubbing the skin—if it doesn’t peel easily, skins have set
• Observing fully collapsed, dry foliage

These signs confirm potatoes are ready for harvest.

Best Conditions for Harvesting

Harvest maincrop potatoes:

• On a dry day
• When soil is not waterlogged
• Before frost is forecast

Dry conditions reduce disease risk and improve storage life.

How to Harvest Maincrop Potatoes Properly

Use a garden fork and lift carefully well away from the plant to avoid stabbing tubers. Handle potatoes gently and avoid dropping or bruising them, as damage shortens storage life.

Curing Potatoes After Harvest

After lifting, allow potatoes to cure for 7–14 days in a cool, dark, well-ventilated place. This helps skins toughen further and allows small wounds to heal before storage.

Which Potatoes Should Be Stored?

Only store potatoes that are:

• Undamaged
• Disease-free
• Fully dry

Any cut, bruised, or scabby potatoes should be used first.

When Not to Delay Harvesting

Harvest immediately if:

• Blight is present
• Heavy rain is forecast
• Frost is imminent

In poor conditions, lifting slightly early is better than losing the crop.

Final Thoughts

Maincrop potatoes should be harvested once foliage has fully died back and skins have set, usually from September onwards in the UK. Correct timing, gentle handling, and curing are essential for long-term storage success. When in doubt, harvest rather than risk weather damage.