Hoya lockii is a captivating and relatively recently described Hoya species, prized for its distinctive white, star-shaped flowers and charming fragrance.
 
Hoya lockii is endemic to Vietnam, meaning it is found nowhere else in the world. It was discovered in the Thua Thien-Hue Province of central Vietnam, specifically in mixed forests at an elevation of around 1,000 meters. It grows as an epiphyte, often found on large old trees in sunny canopy areas.
The species was discovered in 2011 and formally described and published in 2012 by V.T. Pham and L.V. Averyanov. It was named in honor of Vietnamese plant botanist Professor Phan Ke Loc. Sadly, Hoya lockii is considered very rare and endangered in its native habitat, known only from a single population of fewer than 50 mature specimens, primarily due to deforestation and human activities.
 
The original publication details are:
Pham, V. T., & Averyanov, L. V. (2012). New Species from Vietnam-Hoya lockii (Apocynaceae, Asclepiadoideae). Taiwania, Vol. 57, No. 1, pp. 49-54.
A link to the publication is available via the International Plant Names Index (IPNI): https://www.ipni.org/n/77118408-1. The paper can also often be found on academic platforms like ResearchGate or through direct searches for "Taiwania 57: 49".
 
Key Characteristics
Leaves: Hoya lockii has smooth, dark green, elliptic to lanceolate leaves, typically measuring up to 15 cm long and 4 cm wide. They may have small amounts of silver splash. The plant is pubescent (hairy) throughout, except for the leaf blade and the corona of the flower.
Growth Habit: It is described as an epiphytic undershrub with erect stems, growing 40-80 cm tall. While it can have an upright or bushy growth, it may also trail, making it suitable for hanging baskets or as a compact potted plant.
Flowers: The flowers are the most striking feature. They are stunning, pristine white, star-shaped, and quite waxy, measuring about 2 cm in diameter. They are borne in umbels (clusters) of approximately 8 to 25 flowers. The corolla lobes are described as white-opalescent and the corona is also white or light pinkish. The flowers are notable for having a fragrance, often described as a sweet lemon-mint scent during the day, which can intensify to a strong chocolate scent in the evening or night. They are quite durable, often lasting up to 3 weeks.
Relationship to other Hoyas: It is considered closely related to Hoya multiflora due to similar erect shoots, leaf venation, shape, and size. However, H. lockii differs by being pubescent on most parts of the plant (except leaf blade and corona) and having opalescent white corolla lobes and mucronate (pointed) corona lobe apexes.
 
Care Requirements for Indoor Cultivation
Light: Prefers medium to bright, indirect light. It can tolerate a few hours of gentle direct morning sun but should be protected from harsh afternoon sun to prevent leaf burn.
Watering: Allow the soil to dry out a little between waterings. While it prefers consistent moisture, it is crucial to avoid overwatering and soggy soil, which can lead to root rot. Reduce watering frequency in winter.
Humidity: Thrives in moderate to high humidity. Aim for above 50% humidity if possible.
Temperature: This is an intermediate Hoya, best suited to temperatures between 15−35∘C It is not cold-hardy and should be protected from temperatures below 10∘C 
Soil: Requires a very well-draining potting mix.
Potting: Like many Hoyas, it prefers to be somewhat root-bound, which can encourage flowering. Repot only when necessary, typically moving up just one pot size.
 
Tips
Fragrance: If you are interested in its reported chocolate scent, try to observe the plant in the evening hours.
Conservation: Given its endangered status in the wild, responsible sourcing from cultivated plants is important.
Ease of Growth: Unlike some more finicky Hoyas, Hoya lockii is often reported as being relatively easy to grow and flower, even from cuttings.