Techniques
Successional sowing
Also known as: succession sowing
Sowing small amounts of a fast crop every few weeks rather than all at once, so you harvest a steady supply instead of a glut followed by a gap.
Successional sowing (also called succession sowing) is one of the simplest habits a beginner can build, and it quietly fixes the most common problem in a first veg patch: everything ready at once, then nothing for weeks. Instead of emptying a whole packet of seed into one long row in spring, you sow a little, often. A short row now, another in two or three weeks, and another after that. Each batch matures a step behind the last, so you pick a steady trickle through the season rather than a mountain you can't eat followed by a bare bed.
It works best with fast, short-lived crops that you want fresh and keep cropping for only a few weeks. Good candidates are lettuce and cut-and-come-again salad leaves, radish, spinach, beetroot, dwarf (French) beans, peas, and even carrots. Slow or once-only crops like maincrop potatoes, parsnips, leeks and most onions don't need it, because they sit in the ground for months and you harvest them in one go.
The usual interval is every two to four weeks. Quick crops like radish and salad leaves suit the shorter end; slightly slower ones like beetroot and dwarf beans are happy with three or four weeks between sowings. A useful trick is to sow the next batch the day you see the previous one germinate, which paces you naturally without a calendar. If you'd like to understand what's happening underground in those first days, see germination.
In the UK the season runs roughly from March or April through to August. Early sowings often go under a cloche or in a cold-frame to take the edge off cold soil, while the bulk of sowing happens from mid-spring once the ground warms. Stop your main succession around late summer, then squeeze in one last sowing of hardy salad, spinach or winter lettuce in early autumn for picking into the cooler months.
Successional sowing also helps you dodge waste in another way. Crops such as lettuce, spinach and rocket are quick to run to seed in hot, dry spells, a problem known as bolting. By sowing small amounts you only ever have a little maturing at once, so a sudden warm week spoils a handful of plants rather than your entire crop. Keep the new sowings coming, water in dry weather, and you'll have salad and veg to pick from spring right through to autumn.
In a UK garden
In the UK it usually runs from March or April through to August, with a final sowing of hardy salad and spinach in early autumn for a late crop.
Example
Sow a short row of lettuce now, then another in two or three weeks' time, so one row is ready to pick while the next is still filling out.