Hoya obovata

Identification

NParks describes Hoya obovata as a robust vine with thick, leathery leaves. The leaves are obovate, up to 8 cm long and 7 cm wide, mid to dark green above, often with dull gray-silver flecks, and light green beneath ^[3]. Decaisne’s original 1844 description adds that the leaf tip is rounded, only rarely notched, and that the base narrows into a thick petiole. It also notes a glandular callus where the blade meets the petiole, and margins bent back and hairless on both sides ^[1]. The peduncles are short, shorter than the petiole ^[1].

The flowers are white, sometimes tinged pale pink, densely hairy and bent back when fully open. The corona is dull pink, turning rose red toward the center ^[3]. The size is uncertain. NParks gives flowers up to 1 cm across ^[3], but Decaisne described them as about the size of H. carnosa flowers or slightly larger ^[1]. Flora of China gives 1.5–2 cm for H. carnosa ^[6].

Look-alikes. Hoya kerrii is the closest. W.G. Craib separated it from H. obovata by its two-lobed leaf tip and by flowers nearly half the size ^[5]. A plant with rounded, un-notched, obovate leaves therefore fits H. obovata better. Hoya carnosa has ovate to elliptic leaves with a rounded or slightly heart-shaped base ^[6], not leaves that narrow into the petiole.

Naming and trade labels

The accepted name is Hoya obovata Decne., published in 1844 ^{[8, 1]}. No common names appear in the sources consulted. In 1912 Costantin treated H. kerrii as a variety of H. obovata ^[4]. A 2022 checklist of Sulawesi hoyas notes that the relationship between H. obovata, H. kerrii and similar species has still not been studied ^[4]. Plants sold as either name are therefore worth checking against the leaf-tip character above.

Growing it

NParks lists basic growing conditions for this species. Where it says nothing, the notes below use general Hoya guidance from the RHS and say so.

• Light. NParks lists semi-shade ^[3]. General Hoya advice from RHS is a bright spot kept out of hot summer sun ^[7]. See the light guide.
• Water and mix. NParks lists moderate water and a moist but well-drained root zone ^[3]. As general Hoya guidance, RHS suggests a free-draining mix of orchid bark, peat-free compost and coarse perlite in equal parts ^[7]. See the watering guide and the substrate guide.
• Humidity. No species-specific advice was found. As general Hoya guidance, RHS suggests standing the pot on damp gravel in the growing season ^[7]. See the humidity guide.
• Temperature. No institutional source gives a minimum temperature for this species.
• Propagation and pests. NParks lists stem cuttings for propagation and sap-sucking insects as the pests to watch for ^[3]. See hoya pests and water vs substrate propagation.

ASPCA does not list H. obovata. NParks advises avoiding contact with the milky sap, which may irritate skin, and keeping plants away from children and pets because the sap could be toxic ^[3].

Flowering

NParks describes the flowers as fragrant, with a scent similar to that of Hoya lacunosa ^[3]. The sources consulted give no flower count per cluster, flowering season or age at first bloom. For general causes of poor flowering, see why a hoya is not blooming.

Notes on sources

This species is thinly documented. The only full botanical description found is Decaisne’s short Latin one from 1844, written from dried material, which Miquel repeated in 1856 ^{[1, 2]}. The practical details on this page come from NParks ^[3].

The sources also disagree on where it grows wild. WCVP lists Maluku, Sulawesi, Thailand and Vietnam ^[8], while the 2022 Sulawesi checklist treats it as endemic to Sulawesi ^[4]. A plausible reading, not stated by either source, is that the mainland records depend on how H. kerrii is separated from it. No source consulted says whether the leaf veins are visible, so the identifier treats venation as unknown for this species.