This conclusion was originally based on similarities in the morphology of S. perplexum compared with its putative parent species.

Furthermore, if Old Cahaba rosinweed were to be characterized as a subspecies or even a variety, this would necessitate choosing if it had more similarities with S. glutinosum or S. integrifolium.

[4] The ‘lifespan’ of this species (e.g., how long it has existed with few new additions from interspecific hybridization events) has been estimated by studying its distribution compared with its putative parents.

Evidence suggests the species could not have formed post 1885 but no lower bounds on its origin have been proposed, therefore its age is uncertain.

Glandular trichomes are branched and amber colored, the glands secretions give the plant a resinous texture.

The flowers are composite, containing a cluster of fertile disk-florets surrounded by many bright yellow ray-florets averaging around 20 per inflorescence.

This is due to similarities in their morphology, such as the presence of glandular trichomes on the involucral bracts, leaves and stems.

Firstly, S. perplexum has taller stems with more numerous nodes, its leaves are also more lanceolate with shorter petioles and larger blades.

S. perplexum commonly cross-pollinates with other Silphium species in natural environments so is liable to produce hybrid offspring.

[3] This species is endemic to only three counties in west-central Alabama, it has an extremely limited distribution with all populations less than 9 miles from the Cahaba River.

This species is found alongside other tallgrass-prairie plants including grasses such as Andropogon L. spp.

[11] The lack of conservation attention could be due to uncertainty surrounding S. perplexum's species status.