Similar to Hoya edeni King & Hook.f. in its shrubby habit and caudate and curved inner corona lobe processes, distinct by the corona processes (wavy to serpentine in H. medusa versus linear and curved at the tip in H. edeni), corolla shape (urceolate in H. medusa versus rotate with reflexed lobes in H. edeni) and size (8.5–10 mm in H. medusa versus c. 20 mm in H. edeni).

Philippines. Luzon, Cagayan Province, Mt. Cetaceo 500 to 1,000 m, vouchered in cultivation, 07 Feb 2022, M.D. De Leon s.n. (holotype: PNH, sheet no. 258696).

Plant epiphytic pendent shrub, with white exudate in all vegetative parts. Roots basal, fibrous. Stems slender, terete, 1.5–7 mm in diam., green, sparsely puberulent when immature, turning lignified, brown and glabrescent when mature, internodes 2.8–6 cm long. Leaves: petiole stout, usually curved, canaliculate above, flattened towards lamina base, 3–7 mm long, 1.5–2.0 mm in diameter, dark green, sparsely pubescent turning glabrescent when old; blades coriaceous, stiff, flat to slightly curved, variable in shape, oblong, ovate, to elliptic-ovate, 55–90 mm long × 20–34 mm wide; base acute to obtuse, apex acute to acuminate, with a caudate tip, adaxially mid-green, abaxially light green; margins entire, occasionally slightly undulate; adaxially and abaxially sparsely pubescent to glabrescent in older leaves; venation pinnate-brochidodromous, with 4–8 lateral veins on each sides of mid vein, prominent (very pale green) on younger leaves and obscure on older leaves yet clearly visible on dried specimens; colleters one at each lamina base, conical, c. 0.20 mm long, grayish brown. Inflorescence extra-axillary, umbelliform, convex, with up to 11 flowers (occasionally up to 16 flowers in particularly strong cultivated specimens). Peduncle short stout or sometimes sessile, cylindrical, 1.0–3.0 mm long and 1.0–2.0 mm in diam., perennial, sparsely pubescent. Pedicels terete, outer pedicels slightly curved, otherwise straight, 8–10 mm long and 0.5–0.8 mm in diam., light green, lenticellate except the base of the calyx which is pubescent. Calyx lobes oblong, 1.8–2 mm long, c. 0.50 mm wide, reddish, abaxially strigose, adaxially glabrous, basal colleters 1 between each calyx lobes, oblong, c. 0.02 mm long × c. 0.02 mm wide. Corolla basally urceolate, with flat spreading lobes, white, corolla lobes spreading, 8.5 to 10 mm in diam. across the corolla lobes, corolla tube 2.0–3.0 mm long, 4–5 mm in diameter, lobes triangular ovate, 2.5–3.0 mm long, 2.5–3.5 mm wide, apex acute, slightly revolute, margins revolute, corolla lobes adaxially densely strigose, densely hirsute towards the rim and interior of the tube and the column, abaxially glabrous; gynostegium stipitate; column cylindrical, 0.50–0.70 mm high × c. 0.50 mm in diam.; corona staminal 4–5 mm high, c. 3 mm in diam.; corona lobe bulbous-obpyriform, c. 3.5 mm long × 0.5–0.7 mm wide, inner (apical) process caudate, upright, curved, wavy to serpentine, meeting at the center and overlapping, erect above the gynostegium, outer (basal) process obovate, with basal revolute margins, guide rail raised, laterally compressed, prominent at the base of the corona lobes c. 0.80 mm long and extending c. 0.20 mm laterally. Pollinia erect, elliptic-oblong, c. 0.50 mm long, c. 0.22 mm wide; caudicle obovoid, c. 0.10 mm diam; corpusculum oblong, c. 3.0 mm long by c. 1.0 mm wide; ovary ovoid, c. 1.5 mm long, each carpel c. 0.9 mm wise at the base, glabrous. Fruit and seed not seen. Flowers vespertine lasting up to 15 days in cultivation, drying of the inner corona processes begins on the second day causing brown to black discoloration, flowers slightly fragrant, fragrance floral, powdery scent or mild jasmine persistent throughout the day and night.

Figure 1. 

Hoya medusa photographed in cultivation A flower, top view B corolla, from underneath C flower, side view two corolla lobes removed D flower, side view E corona, top view F corona, from underneath G, H corona, side view I calyx and ovaries J pollinarium. (Photographs by R.D. Cuerdo).

The specific epithet refers to the serpentine processes of the inner corona reminiscent of the snake headdress of Medusa in Greek mythology.

Hoya medusa was collected by local collectors in Luzon Island, Mt. Cetaceo and has been in cultivation, circulated by local plant nurseries and plant hobbyists. It was first collected in low montane forest at 500 to 1,000 m where it was growing as an epiphyte in disturbed primary broadly leaf and mossy forest in full sun to part shade.

Figure 2. 

Hoya medusa flowering branch. (Photograph by M.D. De Leon).

The forested area where Hoya medusa was collected is threatened by habitat destruction due to extensive harvesting of trees for local housing and wood-fuel use, destructive farming practices such as “kaingin” (slash and burn farming in Filipino), land conversion and illegal commercial logging. The type locality is a heavily logged forest. Parts of the deforested areas had been converted to agricultural land for crops such as corn, cassava, and vegetables. The western portion of the area is near a protected forested area and remains intact but it is endangered by rapid expansion of agricultural lands by the lowland settlements.

Hoya medusa is only known from a single collection and we do not have information on the extant population size; therefore, the conservation status is proposed as Data Deficient (DD, IUCN Standards and Petitions Committee (2022)) until more information is known about its area of occurrence.

Hoya medusa displays an unusual combination of characters, in particular shrubby habit and corolla urceolate, with flat spreading lobes. This sets it apart from all other shrubby species of Hoya. In the diagnosis we compared it to Hoya edeni because both species are shrubs and present somewhat similar inner corona lobe processes, yet they present very different corolla morphology. The only other species with a similar corolla shape (salverform, with tube narrowly campanulate) is Hoya kachinensis Rodda & K.Armstr. from Myanmar, which is a climber with oblanceolate, ca. 25 long leaves and therefore clearly distinct from H. medusa. Other species that have a somewhat similar corolla shape are Hoya telosmoides Omlor from Borneo, and H. versteegii Simonsson & Rodda from New Guinea, which are both twining climbers. The only species with a tubular/urceolate corolla, somewhat spreading but much reduced corolla lobes as well as a shrubby habit is Hoya manipurensis Deb from India, Myanmar, China and Thailand. Hoya manipurensis has obcordate to triangular laminas and has corolla lobes much shorter than corolla tube, making it once again very easily separated from H. medusa.

Among other species of Hoya occurring in the Philippines Hoya medusa is somewhat similar to Hoya linavergarae and Hoya odorata. The leaf margins of H. medusa are slightly undulate, whereas undulate in H. linavergarae, and flat in H. odorata. The flowers of H. medusa are smaller (8.5 to 10 mm) and basally urceolate with spreading lobes, whereas H. linavergarae and H. odorata have larger flowers (15–23 mm and 13–18 mm respectively), and basally campanulate (H. linavergarae), or rotate (H. odorata) with inflexed corolla lobes. Further, the corolla of H. medusa is densely hirsute inside, whereas puberulent in H. linavergarae and H. odorata. The inner corona processes of H. medusa have a caudate, upright, curved, wavy to serpentine appendage, whereas the inner corona processes of H. linavergarae and H. odorata do not have an appendage.