The plant’s brilliant floral display lingers in the fall |

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You’ve probably seen the bright buttery yellow flowers on this one; the plant is generally very abundant in old agricultural fields and roadsides.

The plants are sometimes present in the thousands, and they can produce a brilliant floral display in the fall, sometimes even with a light frost. This species is found in almost all southern states and as far as the Mississippi Valley.

It is most often seen at low altitudes and is especially common in the coastal plain and Piedmont, not too often in the mountains. It can make quite a fall parade at the edge of an old field, with sunflowers, morning glories, asters and ambrosia.

This plant is part of the bean family, the last name being “Fabaceae” – or “Leguminosae”, if you prefer. The flowers are characteristic, with five unequal petals exhibiting bilateral symmetry.

This architecture is repeated over and over again in different members of the bean family: the larger petal, at the back, is called a “banner” or “standard”. Two narrower petals on either side are ‘wing’ petals, and two even narrower ‘keel’ petals at the bottom embrace and protect the stamens and pistil, which are exposed whenever a large bee lands there, thus effecting pollination.

If you find this plant in bloom, you can easily disassemble a flower with your fingers and you will see this five petal architecture. Some rather romantic botanists (aren’t we all romantic botanists?) Have likened the flowers in the shape of a butterfly and the flowers can thus be called papilionaceous.

After flowering, the ovary of each flower develops into a smooth, swollen pod (or legume), initially green but eventually turning almost black. When the pods are ripe and dried, the shiny black seeds pop off inside and stir easily inside, like miniature maracas. In fact, the genus name of our plant is derived from the rattlesnake genus, Crotalus, in allusion to rattlesnakes.

The foliage of the plant is somewhat unusual for a member of the bean family. Most of the herbaceous members of the family have the leaf blades pinnately divided (on either side of the midrib) into a number of inconspicuous leaflets: think kudzu, clover, and lespedezas, which have three leaflets, but also to glycine, which has about seven to nine. .

Our Mystery Plant is a bit odd in that its leaves are simple, somewhat rounded at the end and tapering to the base, not divided into leaflets at all.

Besides being beautiful, these plants (which are native to southern Asia) are useful in controlling erosion and replenishing soil through the complicated biochemical process of nitrogen fixation: it is sometimes cultivated as a plant. of cover as “green manure”. “

The species was introduced to the southeast for these reasons and, being rather weedy, it has spread. There is a dark side, however – all parts of the plant are found to be somewhat toxic to poultry and livestock, so it’s now kind of a farm responsibility. It’s great, however, for classroom instruction.

(Answer: “” Doorbell box “, Crotalaria spectabilis)

John Nelson is the retired curator of the AC Moore herbarium at the University of South Carolina at Columbia SC. As a public service, the Herbarium offers free plant identifications. For more information visit www.herbarium.org or send an email to [email protected]


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