Successional sowing is a technique used to ensure a constant food supply by sowing seed little and often in batches. The first step is to consider how many lettuces, cabbages, radishes etc you eat per week and plan accordingly, adding a few extra for the inevitable slugs and snails!
Short-lived plants that “bolt” (run to seed) are best sown every two weeks, particularly in warm weather. These include lettuce, rocket, radish, turnips and beetroot, which can be planted by a pinch of seed in a seed tray or directly in the ground. Cabbages (pointed, round and savoy) can be harvested every month in the year if you choose your varieties carefully. Vegetables such as leeks, parsnips, kale and broccoli will weather the harshest winters quite well and can be picked when needed, so successional sowing is less important. Meanwhile sweetcorn, runner beans and tomatoes need as much sunshine as possible so will need to go outside as soon as it is warm enough, and variety will determine cropping time.