Brunfelsia undulata is an upright shrub that can grow to a tree up to 7 m.
It suckers at the base and its foliage is not dense.
The leaves are in small clusters on side branches but can also be single along the main stem.
The petiole is 6 to 7 mm long and the blades range from 6 to 18 cm long.
The ovate to lanceolate blade is from 2 to 4.5 cm wide.
On most leaves both ends taper to a point and there are no hairs.
Inflorescences are a single terminal flower but in cultivation there are often small clusters
on the short side branches or in the upper leaf axils.
The salverform-shaped flowers are on short stalks.
The pale green or yellowish-green calyx is around 2 cm long.
It has 5 short, blunt-tipped lobes that curve outwards.
There are glandular hairs on the outer surface.
The corolla tube, up to 9 cm long and 5 mm wide, is bent at the top.
The limb is up to 6.5 cm wide with 5 round spreading lobes.
The lobes are wavy (undulate) and the edges are crenate (blunt teeth).
Flowers open white and change to cream then yellowish over a few days.
The 2 pairs of stamens insert into the upper part of the corolla tube.
The upper pair just reaches the throat and lie beside the stigma.
The oblong ovary is up to 1 cm long with a single thin style.
The stigma is bilobed.
The fruit are capsules.
B. americana is similar but it has leaves with rounded tips and the calyx lobes have pointed tips.
A widely available cultivar is Brunfelsia undulata ‘White Caps’ which is a 2 m high bushy
shrub with glossy green leaves.
Twice a year it produces large pure white flowers that change to cream.
The petal lobe edges are crenate.