Soybean growth stages

The soybean is a dicotyledonous plant, meaning that it has two embryonic leaves, or cotyledons. Soybean plants exhibits epigeal emergence, as the cotyledons emerge above the soil surface.

How soybeans develop

During germination, an elongating hypocotyl pushes the cotyledons through the soil to the surface. Soybeans generally emerge best if they’re planted no deeper than 2 inches because of the energy required to push the large cotyledons through heavy soils.

After emergence, the green cotyledons open and supply the developing leaves with stored energy, while capturing a small amount of light energy.

Unifoliolate leaves develop first. Two of these single leaves appear directly opposite from one another above the cotyledons. All subsequent leaves are trifoliolates with three leaflets.

sketch of soybean anatomy and various stages of soybean growth

Growth stages

Two distinct growth phases characterize soybean development:

  1. Vegetative (V) stages: From emergence through flowering (Table 1).

  2. Reproductive (R) stages: From flowering through maturation (Table 2).

Plant stages are determined by classifying leaf, flower, pod and/or seed development. Staging also requires identifying the node, or the part of the stem that a leaf attaches to (or was attached to).

A leaf is considered fully developed when the leaf at the node directly above it (the next younger leaf) has expanded enough so the two lateral edges on each leaflet have partially unrolled and no longer touch.

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Seth L. Naeve, Extension agronomist

Reviewed in 2018

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