Family: Bixaceae 紅木科
Common name: Arnatto Dye Plant 紅木 胭脂樹
Origin: Tropical America
Location: Hong Kong Zoological and Botanical Gardens

Annato has pointed leaves and pink, white - or pinkish - white flowers. The small reddish-orange seeds, inside a prickly heart-shaped pod, are crushed and used as food coloring. Approximately 50 seeds grow inside of the pod. Depending on the color of the flowers, the seedpod is either green or red; the seeds have the same coating in both.
The red color is due to apo-carotenoids that are in the seed epidermis.
These seeds are processed to obtain the orange-yellow pigments, bixin and norbixin (carotenoids), as dye for the food -, cosmetic - and soap industries.
This dye is used to color the cheddar cheese and is also used for the coloring of rice.
The used part is the dried pulp of the fruit.

Leaves alternate, simple, three to five-nerved from the base, lanceoate and up to 19 x 11 cm but mostly smaller than this. The leaf margin is entire, the base rounded, the apex long-pointed and the colour often with a reddish tinge especially in dry leaves. The leaf stalks are 2 - 4 cm long and thickened at each end, this is particularly notable at its junction with the leaf-blade and forms a useful dianostic feature.

Flowers appear during August and September, in clusters at the ends of the branches. The flowers are bright pink, showy, about 5 cm across, bisexual and regular. The calyx consists of four or five free, overapping sepals; petals are also five, free, overlapping and twisted in bud; stamens are numerous and free and the ovary is superior, one-celled with many ovules.

The fruit is a red-brown ovoid capsule, breaking open in two to release the seeds. The outer part of the fruit is covered with a dense coat of soft dark red spines.