Classified as a climbing succulent, the hoya originates in the tropical forests of Indonesia, Australia, India and China. Hoyas belong to the Asclepiadaceae family, which consists mostly of stem succulents, according to the Cactus & Succulent Society of America. With the hoya, however, the leaf is the succulent part more so than the stem.
Hoya leaves differ in texture, color, venation and size, depending on variety. The tiny leaves of hoya englenriana are slightly wider than a dime is thick, while to the hoya latifoila leaves measure approximately 10 by 10 inches in width. The hoya coriacea possesses leaves that sometimes reach 2 feet in length. The most succulent of the hoya plants is the hoya kerrii, with heart-shaped leaves notched at the apex, not the base. The hoya teretifolia and hoya linearis possess linear leaves, others perfectly round leaves. Other variable leaf characteristics include smooth and shiny, hairy and veined or without veins.
Flowers of the hoya plants also vary, but they are all shaped like five-pointed stars, according to The Succulent Plant Page website. The flowers grow in umbels, which are clusters of flowers that spring from approximately the same point on stalks of equal length, similar to the ribs of an umbrella. Flowers vary in size from as small as the thickness of a dime in diameter to as large as 3 inches or more. The umbel has varying amounts of flowers; the hoya coriacea has up to 70, each of which measures about three-quarters of an inch in diameter.
Textures of the hoya also vary, with some quite hairy and others shiny and smooth. The blooms of the hoya ranging from pure white to almost black. Some varieties include varying shades of pink. Yellow, brown, yellowish-pink, brownish-red, purple and green constitute just a few colors of hoyas. The closed to a true red hoya, the hoya mindorensis, originates in the Philippines.