Hoya is the latin name for the plants more commonly known as 'wax flowers'. The hoya genus belongs to the subfamily Asclepiadoideae within the family Apocynaceae. There is only one relative to these flowers growing wild in Sweden, namely swallow-wort or 'tulkört' in Swedish (Vincetoxicum hirundinaria).

Hoyas grow wild in an area in Asia delimited by India in the west and Polynesia in the east. The norhern limit is in the southern of China and the south limit is in Australia. Most hoyas have been found in the Philippines and Papua New Guinea Islands. Still, new species are found so it is impossible to know how many there are. The Swedish Hoya Society writes on their website that there might be 200-300 species. Also there are a lot of cultivars/hybrids in cultivation.

Robert Brown was the first to publish a description of a hoya, namely Hoya carnosa. This was in 1809. Hoyas are named after the gardener Thomas Hoy, who was a friend of R Brown. 

Most hoyas are epiphytes, which means that they grow upon other living plants. They use their hosts as support but take no nutrition from them. Many hoyas twine around their hosts, but there are also hanging hoyas and some growing more like bushes. The flowers come in clusters from 1 single flower up to about 100. The hoya genus is very varied; growth habit, foliage and flowers come in many shapes.