Inflorescences in subterminal fascicles or flowers borne singly in leaf axils, often showy and sometimes also night-scented, zygomorphic; calyx campanulate, 5-lobed to approximately half its length; corolla hypocrateriform (having salver-shaped limb above narrow tube), 5-lobed; stamens 4, anthers oblong or elliptical, included and dehiscing longitudinally; ovary bilocular.

As its specific name suggests, B. australis is the Brunfelsia species with the most southerly distribution, the plant occurring as far south as the Argentinian province of Buenos Aires.

[6] The roots of certain Brunfelsia species have been designated as containing compounds hazardous to human health according to a compendium published in 2012 by the European Food Safety Authority.

These compounds include indole alkaloids of the β-carboline group such as harmine, tetrahydroharmine, harmaline, manacine, manaceine, and also derivatives of N,N-dimethyltryptamine and amidines such as pyrrole 3-carboximidamide.

[7] According to early accounts in the literature, symptoms of poisoning by the medicinal species B. grandiflora include dizziness, exhaustion, nausea, hypersalivation, muscle weakness, lethargy, facial nerve paralysis, mouth pains, swollen tongue, numbness in the extremities, paraesthesias (including tingling and feelings of unbearable coldness) tremors, and blurred vision.