Smooth Crotalaria is a perennial herbaceous plant with trifoliate leaves. During its flowering and fruiting period from September to December, each branch tip bears clusters of yellow, butterfly-like flowers, creating a striking sea of blooms. When the pods become mature and dry, the seeds inside detach such that shaking the pods produces rattling sound like a maraca.

Smooth Crotalaria serves as a larval food plant for the butterfly Long-tailed Blue. These butterfly larvae prefer to feed on the flowers and immature fruits of legumes, which is why female butterflies carefully lay their eggs near the calyx or bracts.