When Are My Potatoes Ready to Harvest?

Getting the harvest timing right for potatoes makes a genuine difference to the eating quality, size, and storability of the crop. The right timing varies significantly depending on whether you are growing first earlies for fresh eating, second earlies, or maincrops for storage. The good news is that potatoes give clear signals when they are ready, and a simple test-dig removes all guesswork before you commit to harvesting a whole row.

First and second earlies

First early varieties are typically ready about 10–12 weeks after planting. The trigger for harvesting earlies is flowering — when the plant comes into full flower, it is worth doing a test dig beside one plant to check tuber size. If you find walnut-sized or larger tubers, you can start harvesting. Earlies are harvested young for fresh eating (new potatoes) rather than for storage, so there is no need to wait for the skin to set. Eat them fresh within a few days. Second earlies follow two to three weeks later, at around 13–15 weeks from planting, and follow the same principles.

Maincrop potatoes

Maincrop varieties need the full season — typically 18–22 weeks from planting. The classic signal that maincrops are ready is when the haulm (foliage and stems) has died back naturally: yellowed, collapsed, and dried. At this point the tubers have reached their maximum size and the skins are setting hard (which you can verify by rubbing the skin with your thumb — it should not slip or peel). Allow the haulm to die back completely if possible rather than cutting it, as tubers continue to set their skins for two to three weeks after the foliage dies. Harvest in dry weather if at all possible so tubers go into storage dry.

The test dig

Never harvest a whole row on faith. Instead, push a fork into the soil 30 cm away from the haulm base and lever upward to expose a few tubers from one plant. Check the size and skin firmness. If tubers are smaller than expected, re-cover them and wait another week before testing again. The test dig gives you perfect information about the actual state of the crop with minimal disturbance. Test two or three plants at different positions in the row to account for any variation in plant size or soil conditions.

What happens if you leave them too long

Leaving earlies in the ground after they are ready causes the skins to toughen and the flesh to become starchier — losing the waxy, buttery texture that makes new potatoes special. Leaving maincrops too long risks slug damage, blight infection of the tubers, and the tubers beginning to re-sprout as day length shortens. By late October in most UK gardens, maincrop potatoes should all be in storage. A hard frost will damage tubers left in the ground, so harvest before the first sharp frosts of autumn.