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Early Planted Soybean Starts to Flower (06/30/16)

With the relative early soybean planting this year, and higher than normal temperatures, the soybean plants are transitioning from the vegetative to the reproductive stage.

Early Planted Soybean Starts to Flower

With the relative early soybean plantingplsc.kandel.1 this year, and higher than normal temperatures, the soybean plants are transitioning from the vegetative to the reproductive stage. The first soybean flowers, in some of the research plots, were observed during the last week of June. Typically after 4-6 trifoliolate leaves have been produced, the soybean plant begins the reproductive period. The flowers are self-pollinated. Flowers of soybean are very small (1/4 inch) and are white, pink, or purple. They resemble the flowers of pea or clover, as soybean is also in the legume plant family. From 3 to 15 flower buds can develop at each node of the stem, but not all flowers will result in a pod.

The first flower can be found lower on the stem and this stage is called R1 (R stands for reproductive). The upper nodes will not flower until later. Full flowering is called R2, and is reached when a flower is open at the node immediately below the uppermost node with a completely unrolled leaf. In a field, Individual plants will be at different growth stages. A field is at a designated growth stage (for instance R1) when 50% of the plants have reached this stage.

The soybean plants will continue to develop new leaves during the flowering period. One or two weeks after the first flowers are produced, the first seed pods appear. Most of the pods are set within a few weeks. Some herbicides have a specific growth stage after which application should not take place. Read and observe labels.

Hans Kandel

Extension Agronomist Broadleaf Crops

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