The Roadside Invasion

The unexpected arrival of visitors off the highway has a variety of implications and consequences. Some can be positive and some negative.

The surprise appearance in many cases leaves the host scrambling to react appropriately and recover from their lack of awareness to the potential of a stopover. The soon to arrive holiday season has so many possibilities for unexpected guests showing up seeking lodging and a meal.

Curiously, this also happens occasionally on thoroughfare right-of-ways when unexpected species sprout from the road’s shoulders. Such has been the case recently with the sudden appearance of clusters of Bigpod Sesbania clusters in the region.

Sesbania herbacea, as it is scientifically known, is a native of the southeastern U.S. However, it has only been sporadically documented in many north Florida locations.

This quick growing semi-woody perennial has its good traits. It attracts and supports beneficial insects with its leaf margin glands which secrete sugars.

These yellow Sesbania blooms will likely produce an ample quantity of seed for next year’s growing season. Disturbed soils and full sun (like on road shoulders) provide an ideal growing environment for this weed.

Its seed persist through the winter and are a food source for local game birds. In other regions of the country the seeds are mixed with brown top millet in game plots.

This versatile plant has even been used as a soil improving crop. It is reputed to produce between two and three tons of biomass per acre in 75 days which contains between 90 to 130 pounds of nitrogen.

The plant fibers have been used in a variety of homemade crafts, earning it the common name Hemp Sesbania. Its stems can even be used in paper production if, for some reason, pine trees became extinct.

Unfortunately, this surprise arrival has its problematic features too. The Sesbania species are potentially toxic, containing a compound identified as saponin.

It has been reported that ingestion of the genus has poisoned cattle in Florida and Texas. Despite the toxicity issue, the plant is palatable to cattle and has some nutritional value.

Additionally, this species serves as host for several insects which also attack crops. The biggest issue with this legume is it rapidly becomes an aggressive invasive weed and pushes out other species.

It quickly grows to ten feet tall, and while it has only a few wide reaching branches it grows in dense thickets. It produces yellow or yellowish orange flowers which are streaked or spotted with purple.

Bigpod Sesbania produces elongated seed pods containing 30 to 40 seeds each. The seeds are mottled with orange, brown and greens.

In warmer areas this plant can live 20 years, but is found as far north as New York where is grows as an annual. The southern range of this Sesbania species is Central America and is encountered in south Florida too.

Bigpod Sesbania grows well on disturbed sites with full sun. This can include ditches, fencerows, riverbanks and roadsides in north Florida.

The origins initiating the local germination are often uncertain. It could be all the environmental factors aligned and the seed, which was lying dormant in the soil, sprouted and grew.

Another possibility is an unseen specimen had seed which were relocated to the current germination site. Lastly, seed could have come into the area in fill dirt. 

No matter, unless these unexpected species are removed there will be more next year. Guests then become new residents.

About the author
Les Harrison

Les Harrison is a longtime resident of north Florida, having attended public schools in three counties. He has a Bachelor Degree from the University of Florida in Journalism and a Master’s of Science from Auburn University in Agricultural Economics. He is the author of more than 2000 newspaper and magazine stories and journal articles. During his career, he held positions in private, government and educational (university level) sectors. He holds the title of Extension Agent Emeritus. He can be reached at harrison.gl@gmail.com.

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