Hoya carnosa

Hoya carnosa, the wax plant, is a species in the dogbane family (Apocynaceae). It was formerly considered a member of the Asclepiadaceae, the milkweed family. It is one of the many species of Hoya that are native to Eastern Asia and Australia. It is a common house plant grown for its attractive waxy foliage, and sweetly scented flowers.

The flowers are typically light pink, but may vary from near-white to dark pink; they are star-shaped, and are borne in clusters. The surface of the flowers are covered in tiny hairs giving a fuzzy sheen to them. They are heavily scented and may produce excess nectar that drips from the flowers. Hoyas are unusual in flowering from specialized perennial structures referred to as spurs. These appear from the axils of the leaves and stem; flowers may not be produced when the spurs first appear, but in time buds emerge from the tips. Each season the new flowers are produced on these same spurs and so they should not be harmed or removed.

This species has been in cultivation for more than 200 years and has given rise to many cultivars that vary in foliage form or flowers color.

Hoya carnosa has been shown in recent studies at the University of Georgia to be an excellent remover of pollutants in the indoor environment ^[1]

Cultivation

Hoya prefers bright light, but will tolerate much less. The optimal temperature is 60-85°F (16-30°C). It can be propagated by air layering or by stem cuttings.^[2]

The wax plant benefits from an open potting media that allows some air to get to the roots; typical mixes include large-grade drainage material such as perlite, pumice, or ceramic balls. The plants should be fed regularly with a fertilizer suitable for epiphytic plants.

There is a persistent bit of folklore that Hoyas prefer to be "potbound" - kept in a small pot. It is said that this will hasten flowering.

References

• Hoya carnosa: information in The Plant List

The Hoya Handbook, Kloppenburg, Dale with Wayman, Ann