Green bean seed germination is epigeal. that is the cotyledon is pushed above the soil surface together with the young leaves.
From planting it takes about 6-10 days for the seedlings to appear, depending on the soil temperature. At an optimum soil temperature of 24-30°C the seed will germinate rapidly and the seedlings emerge after about 8 days. Where the temperature is about 30-35°C they will emerge after 6 days. At low soil temperatures such as 15°C seed will germinate but seedlings will only appear after 15 days. Green bean seed will not germinate at temperatures lower than 10°C.
Apart from temperature, the provision of sufficient moisture and the absence of obstructions above the seed will also favour its germination. Hard clods above the seed or a hard crust on the soil surface that form on some soils after heavy rains followed by hot, dry weather will prevent the seedling from breaking through the surface.
These conditions can be overcome by the following methods:
- the soil should be properly cultivated to prevent large clods from forming
- The soil surface may be kept soft with light overhead irrigation until the seedling emerge
- If the soil is raked over the seed in the rows, the water will accumulate in the hollows or furrows, whereas the ridges over the seed will stay relatively loose
- Increasing the organic content of the soil will reduce crust formation.
If possible, check the size of the seed. This is indicated on the bags and the larger the seed the better germination potential. It is actually very easy to calculate which bag has the larger seed. The less the seed count is with the same weight as other bags the larger the seeds are. So you want to buy the lower count seed bags rather than higher seed count.
Bigger seed, better germination, stronger seedlings, higher yields.