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Origin and Habitat: Hoya pubicalyx comes from the Philippines and it was described in 1918.
- Hoya pubicalyx Merr.
Hoya pubicalyx Merr.
Philipp. J. Sci. C 13: 331 1918
ENGLISH: Wax Plant, Porcelain Flower
ESTONIAN (Eesti): Mindoro vahalill
RUSSIAN (Русский): Хойя опушённочашечковая
Description: Hoya pubicalyx is a woody epiphyte or scrambling shrub and can reach a length up to several meters in its tropical habitat. Glabrous through-out excepting the inflorescence. The leaves are narrow and have more or less silver flecks, depending on which variety it is. 'Pink Silver' has a lot of flecks, while 'Red Button' has less making the plant quite decorative when nor blooming. There are many varieties in circulation that bear slightly different coloured flowers all sharing the nice foliage. The colour of the flowers vary from pink-red with white corona to almost black with red coronas, and often the plant produces pink-red, spotted and black flowers in the same umbel and all are quite fragrant.
Stems: Subterete, c. 3 mm across, weakly succulent, smooth, glabrous.
Leaves: Thick, fleshy becoming leathery in time of drought, (8-)10-14(-18) cm long and 2.5-6 cm wide, oblong to oblong-ovate, apex acuminate, base obtuse, shining, concolour, above dark green covered in specks and flecks of grey or silvery white, below paler. Some pubicalyx have new leaves that get red or mixed red/green when young. As these mature they turn green. Petioles often dark red brown. Nerves 4 to 5, thin, arched and merging at the ends.
Inflorescences (umbels): to 9 (or more) cm across, many-flowered, upright, convex. Peduncle stout. Pedicels c. 35 mm, slender, light red and sparsely hairy. Dark olive-green in time of drought.
Flowers: Size of each flower is around 10-18 mm. Calyx-lobes oblong-ovate to ovate-lanceolate pubescent or fuzzy. Corolla-lobes c. 6 mm long, broadly triangular, spreading, apices recurved, light red to to almost black with white margin, densely papillose inside. Corona crown same shade or usually slightly darker, red or red-brown, star-shaped. The flowers produce little nectar, have a strong sweet fragrance and last about two weeks.
Similar species: Its flowers are very similar to those of Hoya carnosa and comparation of DNA sequences suggest that H. pubicalyx and H. carnosa may actually be one species.
Subspecies, varieties, forms and cultivars of plants belonging to the Hoya pubicalyx group
- Hoya pubicalyx Merr.
- Hoya pubicalyx cv. Red Button: Flowers are wine red to dark purple, velvety, coated with translucent hairs, corona red.
- Hoya pubicalyx cv. Royal Hawaiian Purple: clusters with pink-red flowers and also on the same plant you might see clusters that are almost black. Some of the clusters are even mixed pink-red and black.
Bibliography: Major references and further lectueres
5) James Cullen, Sabina G. Knees, H. Suzanne Cubey “The European Garden Flora Flowering Plants: A Manual for the Identification of Plants Cultivated in Europe, Both Out-of-Doors and Under Glass” Cambridge University Press, 11 August 2011
6) Kloppenburg, “The Hoya handbook”, pl. 2 1992.
7) The Hogan 9(1): frontispiece 1987
8) Livia Wanntorp, Alexander Kocyan, Susanne S. Renner “Wax plants disentangled: A phylogeny of Hoya (Marsdenieae, Apocynaceae) inferred from nuclear and chloroplast DNA sequences” Molecular Phylogenetics and Evolution 39 (2006) 722–733
Cultivation and Propagation: Hoya pubicalyx is a Philippine species that is not only easy to grow but quite floriferous. It is an excellent plant for house culture as it stands the extremes of heat and cold better than most plants, and is not easily injured by neglect it can be trained to climb on trellis-work to almost any height, and when in bloom, which continues for half the year, it is a very interesting plant. People often just let them go about their business, trailing around the perimeter of a windowsill and even through-out the house. Some also let them trait out of a hanging pot with their thick waxy leaves looking quite orderly. There are a few Hoya's which make ideal houseplants, Hoya pubicalyx is one of them. It can also handle some cold temps if absolutely dry and does well in just about any light level.
Growth rate: Although the vines can reach lengths of 6 m in the wild, cultivated plants generally extend 1,5-2 m, twisting around supports to which they cling or hanging down in attractive cascades from suspended pots. The all green variety tends to grow more quickly (although it's still slow by most houseplant standards) and is arguably more hardy, but it also comes in a some pretty slow growing variegated varieties.
Potting medium: Bacuse it is an epiphyte benefits from being potted up in a very well-draining and porous potting medium that allows some air to get to the roots; typical mixes include, peat, with some fibrous soil and sand along with large-grade drainage material such as perlite, pumice, or ceramic balls. Often specialized hoya growers either use only chopped coconut husk or a good orchid potting mixture for growing their hoya plants. The medium needs to be moisture-retentive.
Fertilization: The plants should be fed regularly with a fertilizer suitable for epiphytic plants.
Watering: With its succulent qualities it's quite adapt at storing water for longish periods of time between waterings. Water regularly in summer, but do not overwater (wet-sensitively) and let the plants to dry out between watering and then water again. Its roots are easily lost in pots that stay damp for any length of time. Keep quite dry with ample airflow in winter (It would probably tolerate one watering a month). In the rest period no high atmospheric humidity. Care must be taken with watering as they tends to become swollen and untidy in growth habit if given too much water and shade.
Fertilization: During the growing season enrich the soil using a fertilizer rich in potassium and phosphorous, but poor in nitrogen, because this chemical element doesn’t help the development of succulent plants, making them too soft and full of water.
Exposition: This hoya species prefers bright light, but will tolerate much less. Outside half shade to shade (filtered sunlight or afternoon shade tolerated) , inside it will need a reasonably light room in order to actually grow, although it will still get by even in a shadier spot and can be positioned almost anywhere in homes or offices. It subject to sunburn if exposed to direct sun for too long. Tends to bronze in strong light, which encourages flowering and heavy leaves production.
Hardiness: The optimal temperature is 16-30°C (USDA Zones: 10 -12 ), but can handle some cold temps if absolutely dry and does well in just about any light level.
Spring: When winter ends and they begin to grow again, they will require much water and soaking the pots will no longer put the plants at risk for rot. In the spring they will grow well in partial shade and leaving them out in the rain may provide them with the water they need.
Summer: In the summer months they will tolerate heavy rain, but will be just as happy if the season is dry. They will tolerate hot weather outdoors as long as they are kept in strongly filtered light and this will encourage them to flower. They also enjoy some fertiliser. Moving the plants as they are developing buds may cause them to spontaneously abort the flowers all together.
Autumn: In the fall keep them outdoors until the night time temperatures drop below the 10°C.
Winter: Winter care presents no problems at 10° C with plenty of light. In winter be sure to take extra precautions to keep them dry, because damp cool conditions when the plants are resting is an invitation to fungal infections, but - according to temperatures –some occasional lit watering may be useful.
Maintenance: Prune the plant lightly to keep it tidy.
Repotting: In any season it's best to lay the stems out for several days before replanting them and then pot them only in dry soil and withhold any water until they begin to shrivel or start growing again. Re-pot every 2 years.
Pest and diseases: Hoyas are generally fairly easy to grow, especially if kept pest-free. They are very susceptible to stem and root mealy bugs, and damage from these may well initiate fungal attack. Any time when there is a dead or dying stem in the pot it is important to remove it immediately and completely before other healthy stems can become ill too, isolate the healthy parts, dry them off, and re-root them in new compost.
Propagation: It is easily propagated from cuttings. The stems produce aerial roots which roots easily when inserted into a moist medium making it easy to propagate new plants from stem cuttings. Allow cuttings to dry a day before planting. A very good method is to wrap a cutting in moss, keeping it moist until the roots are well started. It can also be increased from seeds sowing in spring in moist, sandy peat moss. Barely cover seeds. Seeds germinate quickly.
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