In the Hoya world, Hoya lacunosa is considered one of the favorites due to its fragrance and its distinctive foliage. It is named after its prominent characteristics of having “lacunose leaves/surfaces (cupped or sunken between the veins). Hoya lacunosa is from the latin word “lacunosa” or lacunose in English.
lacunose Having or full of lacunæ; furrowed or pitted; marked by gaps, cavities, or depressions; specifically, in botany and entomology, having scattered, irregular, broadish, but shallow excavations, as a surface. A lacunose leaf has the venation salient beneath, leaving the surface full of hollows.
Hoya lacunosa belongs to Hoya section Otostemma, which includes the similar species Hoya obscura,Hoya sipitangensis,Hoya walliniana, Hoya nabawanensis, Hoya pusilla and Hoya endauensis.
The species placed in section Otostemma are markedly similar, all having fairly small ovate to lanceolate leaves set closely along the stems and a partially pendant growth habit. The flowers of these species are also quite similar, being comprised of persistent umbels of small, usually revolute* cream colored flowers with pale yellow to red-rimmed coronas. Some species or forms have a pinkish blush to the corollas, as does Hoya obscura and Hoya lacunosa 'Tove'. The plants in this section also have similar fragrances; light, spicy, and reminiscent of carnations and some with fragrance similar to Jasmine flowers.
Hoya lacunosa is a variable species which occurs over a wide range. Early collections seem to have come from Java, but early written descriptions cited the range of H. lacunosa as being the entire "Indian Archipelago", a region which corresponds roughly to present day Indonesia, the island portion of Malaysia, and part or all of New Guinea and Papua New Guinea.
The main distribution area of Hoya lacunosa. Populations of this species may occur farther northwest into northern Thailand and even into India, though present collected material does not bear this out. H. lacunosa is not thought to occur past Wallace's Line (D), nor in the Phillipines. A- Java, the site of the original collections of H. lacunosa var. lacunosa and var. pallidiflora. B- Langkawi Island, the site of Ed Gilding's small- leaved collection. C- southern Thailand, the source of H. lacunosa “Poonsak”.
VARIETIES, FORMS, AND CULTIVARS
As most Hoya growers will have noticed, hoyas can produce dramatically different foliage in response to differing cultural conditions. Hoya lacunosa is among the most marked species in the genus in this respect. Plants received from greenhouses will usually have small, succulent leaves with a teardrop shape, but the same plant in the lower light and humidity conditions of the general home environment will produce leaves that are twice as wide and long, and half as thick .
A) Hoya lacunosa var. pallidiflora, B) H. lacunosa var. lacunosa, C) H. aff. lacunosa from Langkawi Island. The bottom leaf of each pair is typical of growth produced in highlight, high-humidity conditions of a greenhouse. The upper leaf of each pair was produced from the same plant in lower-light, lower-humidity conditions typical of indoor cultivation.
Hoya lacunosa var. pallidiflora differs from the species type in having generally more lanceolate, longer (up to 7cm), darker green leaves with little or no silver speckling. The leaves are typically more acute at the base than var. lacunosa's. The flowers, despite the implication of the variety name (pallidiflora= "pale flowered”), are not noticeably paler than those of var. lacunosa's.
Hoya 'Sunrise' is a hybrid between Hoya lacunosa var. pallidiflora and Hoya obscura. The leaves are larger than in typical lacunosa clones and the flowers are flushed with pink. Hoya 'Sunrise' was produced by Michael Miyashiro.
Hoya aff. lacunosa from Langkawi Island has very small leaves, varying from 1 to 2.5cm. This plant was discovered on Langkawi Island (the largest island in an archipelago just west of the border of peninsular Malaysia and Thailand) by Ed Gilding during a trip with Torill Nyhuus and Ted Green in 1999. This plant has somewhat rounded corona apexes.
Hoya cv “Rebecca” is a cross between Hoya lacunosa Langkawi Island and Hoya obscura and it is created by Antone Jones. It is the product of a pollination by a moth/butterfly. Antone planted the seeds and chose the best seedlings.
Rebecca has a sister cultivar named, Rachel. According to Antone, they are from the same pod but the seedlings looked different so he gave them each a separate name and tossed the rest of the seedlings away. The leaves are 2.5-6 cm long and 1-2 cm wide and have very prominent veins. If this hoya is grown in very bright light/sunshine the leaves will get a lovely red colour. New leaves are often very red, but as they get older the red fades to only a nice red tone.
The almost ball shaped flowers are small, only 4-5 mm in diamater, lovely pink with yellow center. There are 20-30 flowers in each umbel and they last more than a week.The flowers will open 26-30 days from formation of floral buds.
Hoya lacunosa var. lacunosa, the type variety for this species, has leaves with rounded bases and acute to nearly cuspidate* tips. The leaves of this variety are lightly speckled with silver splotches, are of a medium green color, and vary in length from 1.5 to 4cm. Stems and leaves are rather thicker than in variety pallidiflora. With this variety it is easy to see how this species got it’s specific name- “lacunosa”. The flowers are approximately .75cm wide when fully open
before becoming revolute*. The mature flower has all of the corolla petals rolled backwards and under, making a flattened, cream colored ball covered in dense, silvery hair. This mature flower is about .5cm across. The flowers occur in umbels of 15 to 25 flowers. Sometimes, this variety produces leaves that are almost "heart-shaped" as well so it is often confused as the Heart-shaped lacunosa/Hoya krohniana.
Hoya lacunosa 'Tove' is said to have arisen in the Danish nursery of Viggo Larsen and to be named after the proprietor's wife. This exciting cultivar has crisp looking, very acute* leaves, which often display maroon or purplish coloration on new growth. The flowers are blushed with lavender-pink, and the fragrance has a more perfume-like quality than other clones of lacunosa. This cultivar is a rapid grower and blooms early.
Hoya aff. lacunosa “heart-shaped leaf”- The larger flowers (over 1cm) of this clone and its distinctive, heartshapes leaves set this plant apart from other clones. There may be several different plants being traded under this name. This is now traded as Hoya krohniana.
Hoya krohniana is a newly determined Hoya species that has been known in the trade for years as the “Heart-shaped" lacunosa. It comes from the Philippines and was named after Philip Krohn. However, the name Hoya krohniana is still unresolved, so in my opinion, this Hoya needs to remain as "Heart-shaped" lacunosa. I also learned from the training that I attended that a DNA sampling of this species was done and the result showed that it is indeed a Hoya lacunosa.
It is a highly recommended plant that likes it a little cooler than the long-leafed H. lacunosa if you want it to bloom. The heart shaped leaves are 1.5-3.5 cm long and 1.5-2.5 cm wide with raised nerves, especially the vein in the middle. The revolute and fuzzy flowers are creme coloured, almost white, about 8 mm in diameter and you'll find about 15-25 flowers in an umbel. This hoya flowers quite often once it has started and the perfume like fragrance can fill a whole room at night. The flowers last about 4-5 days and produce very little nectar.
Photos - from my own collection ( the big plant is in the Philippines)
Hoya lacunosa “Poonsak” IML1648 was named after the Thai man, a driver and guide for David Liddle, who climbed the tree to collect this form. “Poonsak” has more linear leaves than most clones of H. lacunosa, of a brighter green with more visible veins. This form shows a pronounced tendency to climb, with new shoots usually growing upwards until the weight of the developing leaves causes the branch to bow.
Hoya lacunosa “speckled leaf” is a recent introduction with leaves highly mottled with silver. This plant is most likely a sport of var. pallidiflora, and may revert to plain green leaves occasionally. Solid green branches should be removed to maintain this cultivar’s character. Cuttings of this cultivar so far seem to be quite difficult to root, although this may prove to not be the case when more plants are established in collections under differing cultural conditions.
Hoya aff. lacunosa “giant” is possibly a clone of lacunosa with larger leaves and flowers (1cm when revolute) than other forms, but the determination is still tentative for this plant.
CULTIVATION (from StemmaV1#3)
Hoya lacunosa is a very adaptable and accommodating plant. While rooting is difficult for some forms, established plants grow rapidly and flower over a long period, year round in ideal conditions. Due to these traits, as well as lacunosa’s pleasing form, superb scent and flexible stems (which are less prone to mechanical damage than many other hoyas), this species is one of the few hoya species found commonly in the retail trade. Hoya lacunosa will grow in a variety of lighting conditions and will flower readily even in relatively low levels of light. In brighter conditions, including an hour or two of direct light in the early morning or late afternoon, the leaves of H. lacunosa will display more attractive coloration and form, usually with heavier silver mottling. High humidity also seems to improve leaf form, though plants perform well in regular household conditions. H. lacunosa prefers a moist soil with good drainage, and will more readily tolerate overwatering than drought. This plant does not seem to require being pot-bound to grow and flower well and may in fact become leggy and drop older leaves when roots are overly constricted. H. lacunosa is most widely classified as a cool grower, preferring temperatures from 10’ to 25’C (50’ to 78’F), though it performs well in intermediate (15’ to 35’C (60’ to 95’F)) conditions as well. Growth and flowering may slow or stop when temperatures exceed 30’C (85'F). This species benefits from regular applications of dilute (1/4 to 1/2 strength) balanced fertilizer, and when under-fertilized tends to drop older leaves and flower poorly. Hoya lacunosa is generally grown as a hanging basket plant. All forms lend themselves to this practice. All forms will also climb, given a trellis or support, and are suitable for growing as a mounted plant.
Some collections are more prone to climbing, as is H. lacunosa “Poonsak”, while others, such as var. pallidiflora, readily assume a pendant form and may need some assistance to remain attached to a support.
Cuttings may be started in a 10cm (4”) pot and will eventually need to be moved to a 15- 20cm (6" or 8") pot. Older plants may become quite large and heavy, requiring a 25cm (10") pot. Periodic renewal by starting groups of cuttings in smaller pots will allow most growers to keep this species in a more easily-handled smaller pot. With this species’ many good qualities and its ease of cultivation, this is one of the very finest hoyas, and continues to be justifiably popular.
Note: Most of the information here are from StemmaV1#3 written by Mr. Mark Randal. I found it really helpful and worth sharing.The article has information about Hoya lanceolata as well so I just copy pasted the information about Hoya lacunosa here and added some photos and some additional information.