More information about Quassia amara
The bark and stems are ground into chips for commercial extraction of the Quassimarin, used medicinally for treating fevers, controlling intestinal worms and as an insecticide. It is also used in Angostura Bitters for mixing drinks.

Quassia amara is also quite ornamental, providing small patches of colour when seen from a distance, but with neatly detailed features rewarding closer inspection.  The pinnate leaves are glossy, with a prominently winged rachis, and the red new flush persists as the leaves mature as red veins. 

Flowers are borne sporadically year-round, in long racemes, the crimson petals from a narrow tube, with protruding yellow stamens. The calyx of each fertilised flower persists as a fleshy red cup holding a drupe which ripens to black, somewhat visually reminiscent of the fruit display of the unrelated Ochna serrulata.

The flowers appear to be hummingbird pollinated in their native habitat, and presumably honeyeaters and sunbirds locally have accepted them as a nectar source. The seed can be dispersed by birds and it may naturalise under ideal conditions. Gardeners in the wet lowland tropics close to natural rainforest areas may wish to grow a substitute species, or remove spent flower spikes before seed can develop.

Despite having been grown in botanical collections for many decades, this plant may only be offered by very few and more specialist nurseries.

Other species of Quassia
Quassia baileyana - is a tree to 10m native to NE Queensland’s Wet Tropic rainforests, plus there are apparently four other species found naturally in Australia.
Quassia simarouba (syn. Simarouba glauca) - the Paradise Tree from coastal areas of Central America and the West Indies is a slow growing tree to 15m with glossy pinnate leaves, somewhat whitish on the underside, and flushed red when new.