Thick, glossy leaves on twining stems and domed clusters of waxy, star-shaped flowers that smell sweetest at night. It can flower again and again from the same spurs – if you leave them on.

What it does for you

Its small, star-shaped flowers are shiny and waxy, held in domed clusters, and highly fragrant, especially at night¹. The thick, semi-succulent leaves can store water¹. MBG calls it a long-lived houseplant². It doesn't measurably clean the air: depending on the study, you'd need ten to a thousand plants per square metre³.

Origin & history

In the wild it grows from southern China to Laos and from southern Japan to Taiwan, as a climbing epiphyte or on rocks, mainly in the subtropics⁵. It was first published in 1782 as Asclepias carnosa, and as Hoya carnosa in 1810⁵.

The genus honours Thomas Hoy, gardener to the Duke of Northumberland in the late 18th century². Carnosa means fleshy, after the thick leaves⁴.

Caution

Sources differ. The ASPCA lists it, under the cultivar 'Krinkle Kurl', as non-toxic for cats and dogs⁶, and a University of Nebraska Extension list calls hoyas non-toxic⁷. The University of Zurich's veterinary toxicology database rates the whole plant as very highly toxic in exceptional cases⁸. The main compounds in hoyas are pregnanes and pregnane glycosides, some of which presumably act like heart glycosides. The database rates hoyas as very highly toxic for birds and calls them a dangerous plant for pet birds; in dogs and cats only stomach and gut symptoms have been seen so far⁹. We found no rating by a poison centre for people. The RHS calls the milky sap toxic and advises gloves, as it can irritate the skin¹.

Care

The RHS guide covers hoyas in general; its winter minimum is for this species.

Light. A bright spot, but out of hot summer sun, which can scorch the leaves¹. MBG advises at least half a day of direct sun, NC State bright indirect light^2,4. Good light is needed for flowers; once buds appear, don't move or turn the pot².

Water. From spring to autumn water regularly; keep the compost moist but not waterlogged, or the roots may rot. From mid-autumn to late winter wait until it is fairly dry, but never let it dry out completely¹. NC State says to let the soil dry between waterings and to use water at room temperature⁴. As a rule of thumb, about once a week in summer.

Temperature & humidity. 16–24 °C in spring and summer, away from radiators and cold draughts; cooler in winter, at least 10 °C at night. It dislikes dry air while growing: stand it on a saucer of damp gravel¹. Spider mites can appear when the air is too dry⁴.

Soil, pot & repotting. A sharply draining mix, such as equal parts orchid bark, peat-free multi-purpose compost and coarse perlite. It can stay in its pot for several years, until the roots fill it; repot in spring into a pot only a few centimetres larger¹. It doesn't mind being pot-bound – just don't repot it while it is in bud or flower⁴.

Feeding. Lightly: every couple of weeks in spring and summer, ideally with an orchid feed, once a month in autumn and winter. Flush the pot with plain water every few months to prevent a build-up of salts¹.

Extras

The flowers are white to pink and hairy, in clusters of up to 30⁴, and they make sticky nectar⁸. Cultivars include 'Krimson Queen' or 'Tricolor', with creamy white to pink margins, and 'Compacta' or 'Krinkle Kurl', with folded, rope-like leaves⁴.