Sow in December

Honestly, very little. Sweet peas can still be sown into modules under cover for spring planting. Chillies and aubergines can be started in a heated propagator if you want the longest possible season. Microgreens on a sunny windowsill are the main productive option — they ignore the calendar entirely and crop in days regardless of the weather outside.

Microgreens are the obvious choice — pea shoots, radish, mizuna, broccoli, mustard, and sunflower microgreens all grow happily on a windowsill, going from sowing to harvest in seven to fourteen days. Herbs like basil and parsley can also be grown indoors, though they will be slower in winter light. Sprouting seeds (alfalfa, mung beans) are another option.

Order seeds now while ranges are at their fullest — the popular varieties sell out by February. Plan your beds and consider crop rotation. Clean and disinfect pots, modules, and trays. Sharpen and oil tools. Check that any seeds you have stored are still in date and viable — germination rates drop over time. December planning makes for less stress in March.

Hardy annuals and sweet peas sown in September or October will be sitting dormant or growing very slowly through December. Keep them in a cold frame or unheated greenhouse with good ventilation — stagnant damp air causes more losses than cold does. Water sparingly, only when the compost is genuinely dry. They will surge into growth in February.