Why Are My Bean Seeds Not Germinating?

French beans and runner beans are warmth-demanding crops that refuse to germinate reliably in cold soil. Unlike peas or broad beans, which tolerate cool spring conditions, these beans (Phaseolus species) originate from warm climates and require a minimum soil temperature of 10°C — ideally 12–15°C — before germination proceeds at a useful pace. Seeds sown into cold, wet soil in early spring almost always fail: they absorb water but cannot metabolise their seed reserves fast enough, and in wet conditions they rot before they can sprout.

Temperature is the main factor

Bean seeds need soil temperatures consistently above 10°C to germinate, with 12–15°C giving reliable, fast germination in seven to ten days. At 10°C germination takes two to three weeks and losses to rot are higher. Below 10°C, germination is unreliable and seed rot is the most likely outcome, especially in heavy soils that retain moisture. In most of the UK, outdoor soil temperatures do not reliably reach 10°C until late May — which is why the traditional outdoor bean sowing time is late May to early June, not April.

Sowing depth

Bean seeds should be sown 5 cm deep — deep enough that they do not dry out, but not so deep that the emerging seedling cannot reach the surface before its seed reserves are exhausted. Seeds sown too deep (8 cm or more) in cold, slow conditions may exhaust their energy reserves before the shoot reaches light. Seeds sown too shallow (1–2 cm) dry out rapidly in warm weather. Five centimetres is the reliable standard for both runner and dwarf French beans.

Seed viability and mice

Old beans seeds lose viability quickly — beans more than two years old may have very low germination rates even in good conditions. Always use seed from the current or previous season for reliable results. Also check whether seeds have been physically removed — mice find large bean seeds very attractive and will excavate an entire row overnight, leaving no trace above ground. A row that should have emerged and has simply not appeared is worth carefully digging to see whether seeds are still present, rotted in place, or missing entirely.