Primer on Dry Bean Growth and Maturity
June 19, 2006
Two basic plant types are found in dry edible beans, bush (determinate) or vining (indeterminate). Here’s the key agronomic differences between bush and vine types:
Bush type (determinate) – Stem elongation ceases when the terminal flower racemes (flower cluster) of the main stem or lateral branches have developed.
Vine type (indeterminate) – Flowering and pod filling will continue simultaneously or alternately as long as temperature and moisture permits growth to occur.
Varieties may be classified as either – for example, a quick glance at various navy varieties will find both bush and vine types. In addition to the distinction between bush and vine plant types, four plant growth habits are generally referred to:
Type I – Determinate bush
Type II – Upright short vine, narrow plant profile, three to four branches
Type III – Indeterminate, prostrate vine
Type IV – Indeterminate with strong climbing tendencies.
There are two basic stages of growth: vegetative and reproductive. Vegetative stages are determined by counting the number of nodes on the main stem beginning at the unifoliate leaf node (V1).The reproductive stage begins when the first flower opens, and is described and characterized by observing pod development and seed fill within the developed pod.
At the time of first bloom (R), secondary branching begins in the axis of lower nodes which will produce secondary groups of blooms or pods. It is important to follow the main stem, which is readily discernible on both determinate and indeterminate plants.
A node is counted when the edges of the leaflets no longer touch. A bean plant may have the same number of nodes at two locations but may differ in height because of the distance between the nodes.
The flower of the dry edible bean is typical of all legumes, although flower color varies with cultivars. Beans are normally self pollinated with less than 1% natural crossing.
Immature pods of most cultivars are green, turning yellow, and then light brown or tan as they mature. An exception is black beans where some varieties may have light purple pods. Pods of the navy bean are more cylindrical as compared to the longer, wider and more flattened pod typical of the pintos.
The dates on average days from planting and days between stages is outlined in the following table, but keep in mind that it can be very broad, and will vary from year to year and variety to variety. A number of factors can affect growth and development, including insufficient/excessive soil moisture, high temperatures during flowering which delays pod set, or low temperatures during maturation. Maturity of a variety may also be extended by preplant herbicide injury, excess of or lack of certain plant nutrients, low plant stands, beans following alfalfa in a rotation, or damage from hail. – Adapted from North Dakota State University Extension Dry Bean Production Guide.
Four key growth periods in the life of a dry bean plant
• Germination and stand
establishment (V1 to V2)
• Rapid vegetative growth
(V3 to V8)
• Flowering and pod
development (R1 to R4)
• Pod fill and maturation
(R5 to R9)