Kabocha Squash
Squash & Pumpkin in the UK

You want to get your squash and pumpkins started indoors, usually around April or May. I always sow them on their edge, about 2cm deep, into individual small pots with some proper seed compost. Pop them somewhere warm, like on a sunny windowsill or in the greenhouse, and they'll germinate in a week or so. Don't rush them out, mind, they need a good start before facing the cold.

Once your seedlings have a few true leaves, they'll be ready for a slightly bigger pot if they're getting crowded. You'll need to harden them off for a week or two, gradually getting them used to the outside, before planting them out. Don't even think about putting them on the plot until all risk of frost has well and truly passed – that's mid to late May up here in the North East, earlier down south. Give them plenty of space, like 90cm to 1.5 metres between plants, in some rich, well-prepared soil.