Potato Chitting Calculator — Seed Potatoes & Timing

Chitting means placing seed potatoes in a cool, light spot (like an egg box on a windowsill) to develop short, sturdy shoots before planting. This gives them a head start.

Start chitting about 4-6 weeks before planting. First earlies plant out in late March, so chit from early-mid February; maincrops plant from mid April, so chit from early-mid March. Seed potatoes are ready once the sprouts reach about 5cm.

At the default average of 60g per tuber, expect roughly 16-17 seed potatoes per kg. Larger seed tubers of about 80-100g give around 10-12 per kg, while small 35mm tubers run nearer 18-20 per kg. UK seed is usually sold in the 35-55mm grade.

Plant seed potatoes 10-15cm deep with shoots facing upward. Earth up (mound soil around stems) as they grow to prevent tubers greening and to boost yield.

Chitting gives the biggest benefit to first and second earlies, where an early start brings the harvest forward. Maincrops grow for longer in the ground, so chitting is optional and often skipped — they still crop well planted straight from the bag in mid April.