Soybeans require early spring plantings similar to other summertime crops. Harvest to Table recommends that gardeners sow soybeans two to three weeks after the last frost, when the soil warms to around 60 F. This planting gives soybeans the full summer and fall season for growing and ripening.
As with other beans, gardeners harvest some soybeans when they're green and some when they're mature. The North Carolina Soybean Producers Association states that soybean plants flower in June, July and August, and produce beans soon after. Harvest to Table clarifies that beans will be ready for "green" picking 45 to 65 days after planting.
Mature beans are available in October to November, according to the North Carolina Soybean Producers Association. These mature beans are used as dry beans, for mashing and drying instead of raw eating.