Hoya is a genus formerly in the milkweed family, now in the dogbane family Apocynaceae. There are at least 300 species, all native to the Old World. Almost all are vines, and range from thin-leaved delicate tropicals to semidesert succulents. This month’s featured species is one of the most succulent of all.
Hoya pachyclada (Figure below) does not vine; it is much slower growing than almost all other hoyas. Stems are usually short and densely clothed with very thick leaves. If overwatered and overfed, however, it will produce lengthy stems with long internodes. The leaves continue to thicken over several years. Old leaves may be more than a quarter- inch thick. Plants bear good-sized umbels of white flowers in summer (Flower to left). This species is native to dry tropical forest in Thailand, where it is typically an epiphyte on trees. It grows well in a humus-rich potting medium. Keep it in a very small pot. Overpotting will usually result in a rotted plant. It can be grown outdoors in Tucson most of the year, tolerating heat quite well in at least half shade. (Despite its hard succulent leaves, it does not like desert sun.) It can also tolerate cool weather, but keep it well above freezing in winter. Like many desirable plants, this one is a challenge to find. Even nurseries specializing in hoyas often don’t have it, probably because it grows and propagates so slowly.