Sesbanias are tall, scrawny weeds in the pea and bean family, the Fabaceae. Their shape and compound leaves are said to resemble a young Mimosa sapling or a Wild Senna. Sesbania vesicaria (Bagpod) has become common in the Falls Lake region, but Sesbania herbacea is a relatively new arrival. Sesbania herbacea has colorful common names like Danglepod, Coffeeweed, and Colorado River Hemp. It is a native annual with a spotty distribution in North Carolina, occurring and sometimes colonizing areas where it has been accidentally introduced. It can even hang on as far north as Massachusetts, far from its normal home in the southern coastal plain. From a distance, its form appears insubstantial, melting into the green of background plants, as illustrated by the following photo.
The stem is round and smooth, with a distinct gray bloom. A bloom is a waxy or powdery coating on the surface of a stem that can easily be wiped away by the touch of a finger. The bloom is especially noticeable on S. herbacea.
S. herbacea has alternate, compound leaves with large numbers of opposite leaflets. The high number of leaflets give the leaves a feathery appearance.
A closer look at a leaf blade reveals, below, that the opposite leaflets on this plant often become alternate as the leaf develops.
The outer surface of the petals of the unopened flowers are a rich, red color. Flower color varies greatly among Sesbanias, and is not a reliable indicator of species. The flowers of this particular plant consistently did not begin to open until 1:00 pm, and were not fully open until 3:00 pm.
The orange upper 3/4ths of the flower is called the banner. The yellow inner part of the banner petals are influenced by the outer red, making the petals appear orange. The pure yellow petals drooping straight down are called the wings. In the second photo below, the reddish structure called the keel can be seen between the two yellow wings. The keel petals enfold the pistil and stamens. These flower structures are typical of members of the bean family, Fabaceae.
Long, sickle-like fruits or pods begin to extend from the flowers that have finished their bloom. These sickle-like pods are the easiest way to distinguish Sesbania herbacea from its close relative Sesbania vesicaria.
Below is an isolated view of the young, developing pods.
The pods of Sesbania vesicaria (Bagpod) are completely different from those illustrated above. Bagpods, as the name implies, have short, compact pods that contain only 2 large seeds each. See below.
To compare the flowers and fruits of these two close relatives, check out this link to an article on Sesbania vesicaria.