A sowing calendar is the most useful thing a new grower can have and the easiest thing to follow too literally. The dates below are drawn from RHS growing guides for each crop, and they describe a typical UK season. What they cannot know is your soil temperature, your altitude or how far north you are, and those matter more than the number on the calendar.
Two rules to hold alongside the table. Northern gardens generally run two to three weeks behind southern ones: the RHS puts the safe outdoor sowing point for runner beans at around mid-May in the south and early June in the north, and that gap applies to most tender crops. And soil temperature beats date every time. Runner beans want soil at 12°C, courgettes want 18 to 21°C to germinate indoors, and a cold late spring pushes everything back regardless of what the packet says.
The calendar
Indoor sowing below assumes a windowsill, propagator or unheated greenhouse rather than a heated glasshouse.
| Month | Sow indoors | Sow or plant outdoors | Harvest |
|---|---|---|---|
| January | Little. Start chitting first early potatoes in milder areas from late January | Garlic, if the ground is workable | Leeks, kale, winter salads under cloches |
| February | Lettuce in early February; greenhouse tomatoes from late February; early carrots under protection | Broad beans in mild or sheltered sites | Leeks, winter greens |
| March | Outdoor tomatoes from late March; leeks from late winter | Broad beans, leeks in a seedbed, lettuce from late March, first early potatoes from late March | Overwintered leeks, spring greens |
| April | Courgettes from April, runner beans from mid-April | Carrots from April, leeks, lettuce, second early potatoes early to mid-April, maincrop from mid-April | Rhubarb, early salads |
| May | Late courgettes and runner beans | Runner beans from mid-May in the south, courgettes late May, leeks, lettuce, maincrop potatoes to early May | Broad beans from late spring, autumn-planted garlic from late spring |
| June | Nothing much. The greenhouse is full | Runner beans in the north to early June, courgettes, carrots, lettuce. Transplant leeks when pencil thick | First early potatoes, broad beans, lettuce, garlic |
| July | Nothing | Last carrot sowings to early July, lettuce to late July | Second early potatoes, runner beans from mid-summer, tomatoes from mid-summer, courgettes |
| August | Nothing | Lettuce in early August for early winter under cloches | Maincrop potatoes from late August, beans, courgettes, tomatoes, spring-planted garlic |
| September | Nothing | Winter lettuce varieties in September or October | Maincrop potatoes, leeks, late beans, remaining tomatoes |
| October | Nothing | Garlic from mid-autumn, broad beans in mild areas | Maincrop potatoes to October, leeks, autumn salads |
| November | Nothing | Garlic, broad beans in mild areas | Leeks, kale, winter salads |
| December | Nothing. Plan next year instead | Garlic to early winter | Leeks, winter greens |
The crops behind the calendar
It is worth knowing where a few of those dates come from, because the reasoning transfers to crops not listed.
Potatoes. The RHS advises chitting from late January in milder areas and up to early March in colder ones, taking four to six weeks. First earlies go in around late March, second earlies early to mid-April, and maincrops mid-April to early May. Harvest follows the same order: first earlies in June and July, second earlies in July and August, maincrop from late August through October.
Garlic. Plant from mid-autumn to early winter, because garlic needs one to two months at 0 to 10°C to form a decent bulb. Autumn-planted garlic is ready from late spring to early summer, spring-planted from mid-summer to early autumn. This is the one crop where planting late genuinely costs you the harvest.
Broad beans. The main sowing window is March, April and early May, with October, November or February sowings possible in milder parts of the UK or very sheltered sites. Harvest runs from late spring to late summer.
Carrots. The main season is April to early July, with early varieties in February or March under protection. Roots are ready roughly 12 to 16 weeks after sowing, and baby carrots in as little as four to six weeks.
Leeks. March and April are the prime sowing months, with later-cropping varieties sown in May and June. Transplant when the seedlings are about 20cm tall and pencil thick. Full-sized leeks take around six months, and late varieties will stand in the ground through winter and into spring, which is what makes them so useful in the hungry gap.
Successional sowing is what turns a glut into a supply
The single biggest improvement most people can make is to stop sowing a whole packet at once. The RHS advice for lettuce is to sow a short row every fortnight to give non-stop harvests and avoid gluts, and the same principle works for radishes, salad leaves, beetroot and dwarf beans.
Here is what that looks like in practice. Loose-leaf lettuce is spaced about 15cm apart and is ready in as little as four to six weeks. A one metre row therefore holds about seven plants. Sow one metre every fortnight from late March to late July and you get roughly nine sowings, around 60 plants in total, cropping continuously from early May until the autumn. Sow all nine metres in one go in April and you get 60 lettuces in the same fortnight, most of which bolt before you eat them.
You can lay this out properly in our garden planner, which will hold the bed layout and the spacings so you can see how many plants a row actually gives you before you sow anything.
Reading the calendar against your own Garden
- Keep a diary. One line per sowing: date, crop, variety, where. After two seasons your own records beat any national calendar, because they are measuring your garden.
- Buy a soil thermometer. They cost very little and they answer the only question that matters in April and May.
- Use protection to shift the dates. Cloches, fleece and a cold frame reliably buy a couple of weeks at each end of the season, which in the north is the difference between a crop and a disappointment.
- Do not sow into cold, wet soil. Seed sown a fortnight late into warm ground routinely overtakes seed sown on time into cold ground, and it rots less.
- Read the packet as well. Varieties within a crop differ, sometimes by weeks, and the breeder knows their own variety better than a general calendar does.
This is general growing information rather than advice for any particular garden, and the RHS pages for each crop carry the full detail including varieties and problems. If you are starting from scratch, our beginner's guide to a UK vegetable garden covers site, soil and the first year, and our low-maintenance article is worth a look if the calendar above already sounds like more than you have time for.