III. Growth Habit

Field pea is an annual cool-season legume (pulse) crop. Field pea is well adapted to cool, semi-arid climates. Field pea seed will germinate at a soil temperature of 40 degrees F. Emergence normally takes 10 to 14 days. Field pea has hypogeal emergence in which the cotyledons remain below the soil surface. Seedlings are tolerant to spring frosts in the low 20s and even if injured by a prolonged frost, a new shoot will emerge from below the soil surface. Pea roots can grow to a depth of 3 to 4 feet; however, over 75% of the root biomass is within 2 feet of the soil surface. A relatively shallow root system and high water use efficiency make field pea an excellent rotational crop with small grains, especially where soil moisture conservation is critical.

Field pea is an herbaceous plant and the stems grow to a length of 2 to 4 feet. A leaf consists of one to three pairs of leaflets with a terminal, branched tendril. Leaves are pale green. 

Field pea is of the indeterminate (climbing) type or determinate (bush or dwarf) type. Indeterminate flowering varieties will flower for long periods and ripening can be prolonged under cool, wet conditions. Indeterminate varieties have longer maturity ranges, generally varying from 90 to100 days. Determinate varieties will flower for a set period and ripen with an earlier maturity of 80 to 90 days. Flowering usually begins 50 to 60 days after planting. Flowering normally extends for two to four weeks, depending on the flowering habit and weather during flowering.

Flowers are borne on racemes arising on the axis of the leaves and are highly self-pollinating. Most pea varieties produce white to reddish-purple flowers. Field pea is sensitive to heat stress at flowering, which can drastically reduce pod and seed set. Indeterminate varieties are more likely to compensate for periods of hot, dry weather and are more adapted to arid regions. A flower will produce a pod, about three inches long, containing four to nine seeds. Seeds may have a green, yellow, or cream-colored seed coat. There are two main types of field pea. One type has normal leaves and vine lengths of 3 to 6 feet; the second type is the semi-leafless type having modified leaflets reduced to tendrils resulting in shorter vine lengths of 2 to 4 feet. Peas normally have a single stem but can branch from nodes below the first flower. Determinate, semi-leafless varieties that have good standability are more adapted to wetter conditions.

Field pea is adapted to most regions of the Northern Great Plains. Field pea yields can be compared to, and are very similar to spring wheat on a pound or bushel basis within a specific region.