Description and Adaptation
Pea (Pisum sativum L.) is a pulse crop that is part of the Leguminosae family. It is a cool season annual plant grown adapted to cool temperate zones such as Western Canada.
Pea seed goes through hypogeal germination where the pea cotyledons and seed coat remain below the soil surface (Figure 1). The first two growing points or nodes do not produce true leaves but are called scale leaves which are relatively small, and the nodes seldom emerge completely from the ground. If the young seedling is damaged, re-growth is possible from buds at the base of these scale leaves. Under favourable growing conditions, basal branches will develop from one or both of these nodes by the sixth leaf stage. Under adverse conditions, such as spring frost, regrowth can occur from one or both of these buds at the scale leaf positions.
Once first two nodes are produced, the shoot develops first true leaf at the third node position. First true leaves usually consist of one pair of leaflets and a tendril. An internode follows and then a second leaf is formed at the fourth node. Growth is usually rapid by this stage and under favorable growing conditions; two nodes can develop in as little as seven days. In semi-leafless peas, tendrils replace the leaflets. Most varieties are now semi-leafless with the exception of some of the forage types. The tendrils with the semi-leafless types help the plant intertwine with neighboring plants which increases standability and improves harvest management.
Varieties grown in Saskatchewan are relatively indeterminate, meaning they will continue to grow and flower over an extended period of time until some stress factor induces maturity. Flowers begin to be produced at about the 12th to 16th node stage. Typically one to three flowers are produced at each flowering node. Pea flowers have separate male (stamen) and female (pistil) parts and undergo self-pollination prior to opening. Cross-pollination can occur as a result of pollinators (insects) but is rare. Most pea varieties have white flowers but some forage types can have purple flowers.
Pods develop and within seven to ten days are fully elongated. Over a period of about 24 to 30 days the seeds develop and mature until the dry seed stage is reached. Pods are 4 to 10 centimetre (cm) long and 1 cm wide, and usually contain six to eight seeds. Seed sizes range from 150 to 280 grams per thousand kernels depending on the variety and growing conditions. Bushel weight for dry pea is 60 lb.
Figure 1. Pea seedling node stages
Pea has a relatively shallow root system. Planting peas on cold, poorly drained soils should be avoided, as it favours the development of seedling diseases and root rots. Peas do not tolerate water-saturated or salt-affected soils. Well-drained, clay loam soils are ideal for pea production. Peas can tolerate some hot weather or drought stress during flowering, but yields may be reduced. The best growing temperature range is when daytime highs are between 13°C and 23 °C. Flower abortion can occur at high temperatures (>25°C).
Field pea is well suited to Dark Brown and Black soil zones. It is relatively drought tolerant and can also be grown in the Brown soil zones.
Pea does not tolerate saline soils and should only be grown on non-saline soil. Low pH can inhibit nodulation, reducing nitrogen fixation and plant growth. Most Saskatchewan soils have a pH range suitable for pea growth.