Why Are My Potatoes Going Soft After Harvest?

You dug a fine crop and stacked it in the shed, only to find within a few weeks that the potatoes are going soft, wrinkled, or developing soft spots. Freshly harvested potatoes should stay firm for months if handled and stored correctly, but there are several reasons they break down early. The most common is that the potatoes were stored without being cured first — a simple but crucial step that most home growers skip because it is not widely taught.

The curing step most growers miss

Freshly dug potatoes have thin, tender skin with wounds from the harvest process — fork marks, scrapes, and abrasions that are entry points for rot. Curing allows the skin to harden and minor wounds to heal before storage. To cure potatoes, spread them in a single layer in a warm (15–18°C), dark, humid place with good ventilation for 10–14 days. A garage, shed, or covered porch in early autumn works well. After curing, the skin sets firmly, the wounds callous over, and the potatoes are ready for long-term storage. Potatoes stored immediately after harvest without curing almost always develop rot at wound sites within weeks.

Wrong storage conditions

Even well-cured potatoes will deteriorate quickly if stored incorrectly. Too warm (above 10°C) causes them to sprout and shrivel. Too cold (below 4°C) causes the starches to convert to sugars, which makes them taste sweet and cook poorly. Too humid without airflow encourages mould and rot. Too dry causes shrivelling. The ideal storage is 4–7°C, dark, and with moderate humidity and good air circulation — a cool cellar, insulated garage, or traditional clamp works perfectly. Store in wooden crates, paper sacks, or hessian bags. Never use sealed plastic containers, which trap moisture and cause sweating and rot.

Harvesting potatoes too early

Potatoes harvested before the skins have fully set — which happens naturally as the haulm dies back — have thin, delicate skins that slip off with light pressure and do not store well at all. New potatoes and first earlies are deliberately harvested at this stage for immediate use and should never be stored for more than a few days. Only maincrops with fully set skins store well for months. If you are uncertain whether the skins have set, lift one potato and rub the skin with your thumb — if it slips easily, the potatoes need more time in the ground or you should eat them promptly rather than storing.

Disease in the stored crop

Any potatoes with rot already established — from blight, soft rot, or damage — will spread to neighbouring healthy tubers rapidly in storage. Sort ruthlessly at harvest: discard any tuber with soft spots, discolouration, holes, or any smell. Check stored potatoes every two to three weeks and remove any that are softening or showing signs of rot before the infection spreads. A single rotten potato in a closed box can reduce the whole store to mush within two weeks.