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Origin and Habitat: Hoya obscura is endemic to the southern part of the island of Luzon (Philippines).
Type locality: Irosin (Mt. Bulusan), Province of Sorsogon, Luzon
- Hoya obscura Elmer ex C.M.Burton
Description: Hoya obscura is a small to medium-sized hoya characterized by rather stiff stalks that are not as inclined to twine as most hoyas and medium-sized leaves that are deep green with lighter pinnate veining when grown in shade, but redden considerably when exposed to direct winter sunlight. Extremely floriferous it is definitively one of all-time favourite species with a seemingly never-ending supply of flowers. The small flowers are similar to those of Hoya lacunosa, salmon/pink with a yellow centre and a white flowered form is known. It is a heavy bloomer during the warmer months The flowers are pleasantly fragrant, but the scent is described very differently: "a spiced honey fragrance", "a slight hint of lavender perfume", "a fresh cut lemon fruit sour" or "a buttered cinnamon roll fragrance", the scent wafts a considerable distance especially at night.
Growing habit: Epiphytic to semi-epiphytic in the wild, winy and compact and apparently forming tangled bushes.
Stems: 5 to 8 mm thick, terete, glabrous, dull yellow as they ages, branched from near the root cluster, woody at or near the base and winged at tips, the main branches often opposite and quite rigid.
Roots: Crooked and rigid, ultimately finely rebranched.
Leaves: Opposite, scattered along all the branches, mostly fairly close together along new shoots. Petioles 5 to 15 mm long glabrous, dull brown and grooved on the upper side. Lamina glabrous, smooth lucid and glossy especially on the upper surface, entire, nearly elliptical in smaller leaves, oblong-oval. in larger ones varialbe in size from 2 to 10 cm long and nearly 4 cm wide, gradually tapering to the apex, pointed. Base broadly obtuse to slenderly wedge-shaped. Deep to light green or grayish with very shallowly depressed lighter veining on the upper face when grown in shade, but yellowish brown to reddish when exposed to direct winter sunlight. Lateral nerves faint, 3 to 5 on each half of the leaf blade, quite oblique especially the basal ones, obcurely forked and more or less fused together at their ends, reticulations none. In cultivation the leaves can also take a nice bronze colouring with appropriate fertilizers.
Inflorescence: Many-flowered, flattish, with up to 25(-30) flowers. Peduncle stout, leathery, up to 5 cm long, curved, usually arising from the leaf axils, terminated by a much thickened flower bearing portion. Pedicels glabrous up to 1 cm long, most of them curved finally deciduous, flowers subtended by bracteoles.
Flowers: Small, rotate, hermaphrodite, salmon/pink to brownish, with a yellow centre (a white flowered form is also known). Calyx composed of 5 rotund glassy segments, c.1.5 mm long and wide. Corolla lobes united toward the base, ovate and with acute tips recurved towards the peduncle, semi-transparent, the upper or inner surface densely covered with fine, short hairs creamy white, light yellow to pink and pink. Seen from above, the corolla is flat, roundish to slightly pentagonal and only slightly larger (in diameter) than the corona. Corona light yellow, yellow or reddish at the base of the corona lobes; horns of the corona 5, suberect, small, with minute appendages from their inner basal portion; stamens surrounding the 2 flask shaped erect pistils. The flowers remain open about 6 days.
Bibliography: Major references and further lectueres
1) Plants & Gardens, Volumi 43-44, page 54, Brooklyn Botanic Garden, 1987
2) Wikipedia contributors. "Hoya obscura." Wikipedia, The Free Encyclopedia. Wikipedia, The Free Encyclopedia, 19 Aug. 2014. Web. 24 Feb. 2015.
3) Adolph Daniel Edward Elmer “Notes on Asclepiadaceae.”, In: Leaflets of Philippine Botany, 10 (131): 3543-3599, Manila 1938 Online <http://www.biodiversitylibrary.org/item/6769#page/83/mode/1up> Web. 24 Feb. 2015.
4) Anders Wennström, Katarina Stenman “The Genus Hoya - Species and Cultivation.”, Botanova, Umeå 2008.
Hoya obscura Photo by: Luiza Ferreira
Hoya obscura Photo by: Luiza Ferreira
Cultivation and Propagation: Hoya obscura is an excellent species producing large ornate leaves well suited for baskets.
Requires rain and frost protection in very cold climates and maybe shy to flower if kept too cold. When in bloom, which continues for half the year, it is a very interesting plant. Extremely floriferous.
Growth rate: This is a bushy species that grows really well and strong in optimal conditions, but it is relatively restrained in growth (compared to certain other members of the Hoya genus).
Potting medium: Because 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 no direct sun. 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.
Temperature: The optimal temperature is approximately 12-15 ° C in winter and 30 - 40 ° C in Summer ( Outdoor zone: At least Zone 10, possibly cooler ).
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 12° 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: Hoya 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: This species propagates readily from stem cuttings, whether in water, in soil or in a sterile medium (such as perlite).
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