pronounced: KOST-uss speck-ee-OH-suss
Costus is from the Sanskrit name for the species, Kushtha; speciosus is Latin for showy, beautiful or handsome. This plant is native to south-east Asia, especially on the Greater Sunda Islands of Indonesia. Costus differs from the common ginger by having only one row of spirally arranged leaves.
It is an erect, perennial herb, robust, unbranched, growing to a height of 2 m or more, arising from a rhizome. The leaves are simple, alternate, spirally arranged, attached to the top of a sheath; the blade is oblanceolate to elliptic, 8 – 25 by 3 – 7 cm, the lower surface silky pubescent.
It flowers throughout the year, the flowers borne among fleshy bracts in a dense ovoid to globose terminal head up to about 10 cm long. These bracts are bright red to purple in the usual Costus speciosus, but green in this cultivar, whose name I do not know. The flowers are white, trumpet-shaped, 6 – 9 cm long, apex toothed with overlapping edges. The stamens are petaloid, white with orange-yellow base.
The fruit is generally red, although I have not seen the fruit of this cultivar, and cannot confirm its colour. The seeds are black with a white fleshy aril.
The species reproduces vegetatively by rhizome, birds disperse seeds when they feed on the fruits, and the plant can also be grown from stem cuttings. Costaceae are the only gingers that can be propagated in this last-mentioned way. It has become an introduced invasive species on some Pacific islands, including the Cook Islands, Fiji and Hawaii. It is cultivated in India for medicinal uses. The plant has many historical uses in Ayurveda, the 5000–year–old ancient Indian science of healing. The rhizome has been used to treat fever, rash, asthma, bronchitis, and intestinal worms. In the Kama Sutra it is given as an ingredient in a cosmetic to be used on the eyelashes to increase sexual attractiveness.
“An ointment made of the tabernamontana coronaria, the costus speciosus or arabicus and the flacourtia cataphracta can be used as an unguent of adornment. If a fine power is made of the above plants, and applied to the wick of a lamp, which is made to burn with the oil of blue vitriol, the black pigment or lamp black produced therefrom, when applied to the eyelashes, has the effect of making a person look lovely.”