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Family Asclepiadaceae

Hoya
Hoya carnosa (L. f.) R. Br.
WAX PLANT

Scientific names Common names
Hoya carnosa L. f. Hoya (Engl.)
Asclepias carnosa (L. f.) R. Br. Wax plant (Engl.)
  Porcelain flower (Engl.)


Botany
The plant is a semi-woody, succulent perennial climibing vine. Leaves are glossy, waxy, succulent and grayish green, elliptic to broad-oval, up to 20 cm long. Flowers are in umbels, 3 to 5 inces in diameter, pinkish-white with a red star-shaped crown.

Distribution
Indigenous to Australia, China and the Philippines.
Ornamental cultivation.
Popular as a hanging pot plant.

Uses
Folkloric
• No reported folkloric medicinal use in the Philippines.
Others
Air-Purifying Plant: In a University of Georgia study, Hoya carnaso was shown to be good at absorbing VOCs. VOCs are volatile organic compounds, contaminants emitted by various common household items. More than 300 have been identified – carpets, wood panels, paints, pets, formaldehyde, benzene and toluene from old books, newspapers, waxes and adhesives.

Studies
Volatile Compounds: Study isolated volatile compounds from the flowers of Hoya carnosa: methyl butanal, ethylbenzene, o-xylene, p-xylene, benzaldehyde, 6-methyl-5-heptan-2-one, benzyl alcohol, linalool, 2-nonen-1-ol, phenylethylalcohol and 2-(E)-noneal.

Counterpoint
Can plants control indoor air pollution? Recent reports in the media and promotions by the decorative houseplant industry characterize plants as "nature's clean air machine", claiming that National Aeronautics and Space Administration (NASA) research shows plants remove indoor air pollutants. While it is true that plants remove carbon dioxide from the air, and the ability of plants to remove certain other pollutants from water is the basis for some pollution control methods, the ability of plants to control indoor air pollution is less well established. Most research to date used small chambers without any air exchange which makes extrapolation to real world environments extremely uncertain. The only available study of the use of plants to control indoor air pollutants in an actual building could not determine any benefit from the use of plants69. As a practical means of pollution control, the plant removal mechanisms appear to be inconsequential compared to common ventilation and air exchange rates. In other words, the ability of plants to actually improve indoor air quality is limited in comparison with provision of adequate ventilation.
     While decorative foliage plants may be aesthetically pleasing, it should be noted that over damp planter soil conditions may actually promote growth of unhealthy microorganisms.

Availability
Ornamental cultivation.


Additional Sources and Suggested Readings
(1)
Study identifies best air-purifying plants / Sharon Dowdy / University of Georgia / College of Agricultre and Environmental Sciences
(2)
Determination of Volatile Compounds from Hoya carnosa Flowers (Aslepiadaceae) / Jankana Burana-osot and Gerhard Buchbauer / Thai J Pharm Sci. 26 (1-2):39-44 (2002)
(3)
Indoor Air Pollution: An Introduction for Health Professionals / Can plants control indoor air pollution? / Environmental Protection Agency


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