Common name : Ms. Burton Hoya
H. burtoniae was named after Ms. Christine M. Burton, an American collector and researcher of Hoya, 81 years after the type specimen was collected by Mr. Loher in Montalban, Rizal a province in the Luzon Island, Philippines in September 1909. It is included as an endangered species in the Department of Environment and Natural Resources Administrative Order (DAO) No. 2007-01.
H. burtoniae has a velvety stem that forms aerial roots below the node. The leaves are thick and leathery, and clothed with soft, fine, minute hairs on both surfaces. They are olive green with prominent purplish margins and purplish undersides due to plentiful ANTHOCYANIN content. The leaves are more regularly ovate-elliptic (rather than long and narrowly lanceolate to narrowly oblong or oblanceolate), are rigid, are covered on the upper surface with closely-spaced velvety granules but less pubescent and granular on the lower surface, and measure 51.0mm long and 25.0mm wide. The margins are revolute, the bases attenuate, and the tips obtuse or somewhat acute. Venation is obscure.
The flat umbel, measuring 60.00 mm across, is composed of up to 45 loosely arranged but rigid flowers that face the ground. Individual flowers measure 7.00 mm in diameter, have a recurved corolla that is smooth outside and is covered with soft, fine hairs inside.
There is a clone whose leaves lack the red spots underneath. However, leaves with green undersurface may occassionally be found within a clone that has purplish undersides. It is sometimes being sold in the market as H. burtoniae but it is not the real H. burtoniae and should be labelled as H. sp. aff. burtoniae.
Source of info: A collection of Philippine Hoyas and their culture Book series no. 2/2013