Seed Sowing — Getting the Timing Right

The Most Common Mistake

The single most common mistake made by new kitchen gardeners is sowing too early. The instinct to start as soon as possible in late winter is understandable, but leggy, starved seedlings raised in insufficient light are a poor beginning to the season. Cold soil that fails to germinate seeds, or seedlings that sit still for weeks in pots, give no advantage over seeds sown at the correct time.

The Sowing Calendar

Timing is governed by three factors: whether the crop needs indoor propagation, the last expected frost date in your area, and soil temperature.

January–February (indoors only): Onions and leeks (slow-growing and benefit from early start), chillies and peppers (long season required), broad beans (in pots to transplant early).

March (indoors, with care): Tomatoes (8 weeks before last frost), aubergines, sweet peppers, celery and celeriac, early lettuce (for cold frame planting).

April (indoors, and outdoors under cover): Courgettes and cucumbers (3–4 weeks before planting out), sweet corn (2–3 weeks before planting out), basil. Outdoors under fleece: beetroot, carrots, parsnips, peas, spinach, lettuce.

May (outdoors direct): After last frost: beans (French, runner), courgettes, squash. Directly: beetroot, carrots, chard, lettuce, rocket, turnip.

June–July: Successional sowings of salad, beetroot, French beans for autumn harvest. Autumn/winter brassicas sown in seedbed for transplanting.

Soil Temperature

Seeds will not germinate in cold soil. Most vegetables need a minimum soil temperature to germinate reliably:

• Cold-tolerant (5–7°C): Broad beans, parsnips, spinach, lettuce, onions
• Cool season (7–10°C): Carrots, beetroot, peas, brassicas, leeks
• Warm season (12–15°C): Beans, courgettes, cucumbers, sweet corn
• Heat-loving (15–18°C): Tomatoes, peppers, aubergines, basil

A soil thermometer is one of the most useful tools in the kitchen garden.

Successional Sowing

Rather than sowing a whole packet of lettuce or radish at once, sow small amounts every 2–3 weeks from early spring to late summer. This provides a continuous harvest rather than a glut followed by a gap. Mark your sowings in a notebook — memory is unreliable over a long season.