The Bush Allamanda is an upright shrub 2.5 to 3 m high with hairless stems.
The stems and leaves contain an irritant milky sap.
The simple elliptic to obovate leaves are in whorls of 4 (3 – 5) or almost opposite.
On a stalk about 2 mm long the blade is up to 14 cm long and 4 cm wide.
The base is wedge shaped and the tip a short point.
The veins are prominent on the underside and have short stiff hairs on them.
The intramarginal vein is also prominent.
Inflorescences are branched terminal clusters of a few flowers on short stalks.
There are bracts but they fall off early.
The funnel-shaped flowers are 4 to 6 cm long – smaller than A. cathartica.
Flower parts are in 5’s.
The sepals are lance-shaped and remain on the ripening fruit.
The corolla tube is 2.5 to 3 cm long.
The reddish basal part is narrow but with a swollen base.
The upper, longer part of the tube is wider, curved and a pale orange with reddish lines inside.
The flaring, round to ovate corolla lobes are a pure, bright yellow.
The stamens are inserted at the top of the narrow part of the tube.
On very short filaments the anthers open inwards.
Above, below and between the stamens are tufts of white hairs.
The superior ovary has a single style with a large style head.
The anthers converge around, but are not fused to, the style head.
The fruit are capsules that ripen from soft and green to brown and woody.
Roughly round and about 3 cm in size, they are covered in long spines.
The flat brown seeds have a narrow wing around the edge.
The ‘Silver Dwarf’ cultivar is a smaller shrub.
The narrow leaves, in whorls of 4, are a grey-green with a dark green midrib.
The veins, including the intramarginal one, are much less obvious.
The greenish to reddish corolla tube is 2/3 to 3/4 of the length of the flower.
It has a long, narrow base then a wider upper part.
Internally there are reddish lines.
The flaring bright yellow lobes are narrower than those of A. cathartica.