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Feature Story

The amazing world of Hoyas

by Rita T. dela Cruz

Photos by Dr. Monina Siar
January-March 2007
Volume 9 Issue No. 1

 

Dr. Monina V. Siar of the Institute of Plant Breeding, a name that has been greatly identified and associated with Hoyas.

Not many people are familiar with Hoyas and what they actually look like. Some may have seen or chance upon them growing between and among shrubs and trees or along ridge tops or trail gaps, but would be often ignored due to the lack of a better knowledge about this plant. Yes, Hoya is no chocolate (in reference to the famous Goya sweets manufacturer); it is rather a juicy, porcelain-looking flowering plant.

Hoya is colloquially known as wax plant, wax vine, porcelain flower or gap plants and is considered as one of the most horticulturally interesting plants because of its profuse number of species (discovered and undiscovered). Also, due to its unique form, size, texture, and wide variety of its multi-colored blooms.

It belongs to the Apocynaceae family of tropical plants and was discovered by the Scotland-born botanist, Robert Brown (widely known for his Brown Movement). He named the plant after his friend, Thomas Hoy, an English botanist who worked as head gardener for the Duke of Northumberland in England. The word Hoya is the Latinization of Mr. Hoy's surname.

Hoyas are twining vines (but there are also bushes) with oozing milky sap when cut (others have clear sap), waxy leaves, and showy clusters of blooms borne out of the thick flower stalk that resembles an upside-down umbrella. Many of its species are scented.

This plant is common in Australia and Polynesia, the Islands of the South Pacific, Oceania, China, and Southeast Asia. Southeast Asia has the most wide collection of Hoyas. The Philippines alone possesses some of the riches and most diverse Hoya species in the world and are being sought after by collectors and enthusiasts.

Hoyas in the Philippines
Hoyas in the Philippines were discovered as early as the 1900s through Friedrich Schlecter, a German botanist, who was in Manila conducting economic botany in March 1907. With him in this endeavor was the then United States Department of Agriculture (USDA) head in the Philippines, Elmer Merrill, who introduced and sent Schlecter Hoya plants.

Philippine Hoyas are often found in the highest mountain peaks but mostly in low elevated places such as seashore and mangroves. They are light-loving plants so they can also be found among shrubs or tops of trees and other often-ignored places such as gaps in the forest.

According to Dr. Monina V. Siar of the Institute of Plant Breeding-University of the Philippines Los Baņos (IPB-UPLB), most of the Hoyas sold in the world market today have Philippine origin, which is a positive indication of the diversity, rarity, and world class beauty of Philippine Hoyas.

Currently, there are 61 species named and described Hoyas from the Philippines. But Dr. Siar emphasized that this is not all as there are still a lot of unidentified Hoyas species waiting to be discovered and named.

Philippine Hoyas with export potential
The name, Monina V. Siar, has been greatly associated with Hoyas because of her devotion and dedication in studying its various species that are native to the Philippines. In fact, three new species of Hoyas have been discovered together with Robert Dale Kloppenburg of the International Hoya Association (IHA). These are: 1) H. lucyae Kloppenburg and Siar, 2) H. viracensis Kloppenburg and Siar, and 3) H. linavergariae Kloppenburg and Siar.

Dr. Siar believes in the potential of this plant which could bring in better opportunities and market potentials for the country. She said, “If we are to penetrate the world market and make a niche for our Philippine Hoyas, it's important to start recollecting, propagating, characterizing, and trading them.”

With more than 200 species discovered, most of them are native to the country, Dr. Siar identified nine Philippine Hoyas which the country can take good advantage of owing to its export potential in the world market.

Hoya pubicalyx Merrill
This species is easy to grow and a favorite among Hoya enthusiasts. It is characterized by its globular clusters of flowers that come in various colors. Common variants are named depending on the color variations of its flowers (i.e., bright one, pretty one, and red buttons). The leaves vary from densely silver to all green. According to Robert Bedard of Robert Bedard Horticulture, this species makes an excellent pot plant, indoor or outdoor. The flower clusters are spectacular and may bloom with many umbels open at the same time. It is also a repeat bloomer. Another favorable characteristic is its toughness to cold temperature, which means it can thrive colder weather better than most other Hoya species and undoubtedly survive better than the others.

Hoya mindorensis Schlechter
This is considered one of the most beautiful red Hoyas native to the Philippines and is often included among the collections of enthusiasts. The color of flowers ranges from reddish pink to orange with long white hairs giving its corona an unusual background.

Hoya imperialis Lindley
This mangrove-loving plant is a bit different from the usual Hoyas. Its corona is very large and heavy-looking. Its royal purple flowers resemble a royal emblem with vine that is strong with thick stems and leaves. The colors of the flower vary from dull red to purplish red with smell that is similar to Vanda orchid. Its Alba variant was discovered in Palawan, Philippines; it is also the most expensive. Each flower is about two inches and produces 9-12 huge flowers at once. The flowers last for 14 to19 days.

Hoya paziae Kloppenburg
This was named after the wife of Robert Dale Kloppenburg, author of the book Philippine Hoya Species, which has become the bible of Hoya enthusiasts. Physical-wise this species is untidy and shrubby. Its leaves are dark green and its flowers have superb sweet smell.

Hoya heushkeliana Kloppenburg
This is unusual among the Hoyas, with its urn-like feature resembling little bells. The flowers are red and yellow.

Hoya meliflua (Blanco) Merrill
This consists of a large globular cluster of 10-20 flowers with colors that vary from pink to orange to purple. Its leaves are distinct from those of other Hoyas as they are narrow and thick, deep green and with no venation.

Hoya buotii Kloppenburg sp. Nova
One of the unique characteristics of this species is the presence of whitish hair in its creamy yellow flowers and reddish corona. The fully opened flowers look like a starfish. The leaves have venation with thin texture.

Hoya siariae Kloppenburg sp Nova
This woody vine species has deep green and shiny foliage. Its pinkish flowers are small and shiny-looking that one can mistake it for a plastic. Its flowers only open for a day and do not last long. This particular species was named after Dr. Siar in recognition of her efforts and contributions to the study of Philippine Hoyas.

Hoya bicolor Kloppenburg
This is considered the most striking and beautiful among the climbing Hoyas. Its umbel, which consists of 25-40 flowers, is cream colored and yellow corolla with a hue of pink at the tips.

Culture and propagating
Hoyas are easy to grow and for most part, are virtually neglect-proof once mature. They require a well-drained soil, warmth, and lots of humidity. They can be propagated by seed, by stem, roots, or leaf cuttings.

Propagation from stem cuttings is relatively the easiest and most common. This is done with two or more nodes with its leaves at the lower nodes removed. Expert growers of Hoyas warn about cutting its stem since they produce thick, milky sap that can make pruning and propagation a sticky and messy piece of work.

Another means of propagating is through root cuttings best grown with a lot of moisture in coir dust, coconut husks, and crushed fern barks. Putting them in clean and sterile pots is crucial to avoid pests and diseases.

Propagating by leaf cuttings can be a bit problematic as it may take sometime to produce and enhance the roots. Rooting hormone could be used as root enhancer. Often leaves develop roots but do not go on to produce healthy plants.

Another is by seeds. It is advised that only freshly harvested seeds are used for propagating since these seem to germinate better. Germination rate is high if sown in a mixture of coir dust and quarry sand. Once the seedlings start to develop true leaves, repot and plant out separately.

Although regular repotting in fresh soil is beneficial, Hoyas are happy in pots that are too small and soil that is too old. Avoid over-potting since Hoyas are root-bound. They are tolerant to a wide range of temperatures and humidity, thus, they will survive even in low-light conditions. But good, bright light is needed for them to thrive healthy and bloom regularly.

World market potential and demand
With the advent of new technologies and innovative means of communication, selling and buying of Hoyas via Internet is widespread. On both ends, trading becomes cost-effective since growers commonly sell these as cuttings (12 inches long with at least three nodes).

Mostly Hoyas are sold by shipment process with replacement policy for lost plants and consideration for a country's quarantine restrictions and limitations. Others are distributed through dealer-collector method also done through the Internet.

According to Dr. Siar, the top five most expensive Hoyas today are H. imperialis ($25-75), H. paziae ($15-20), H. bicolor ($12-25), H. buotii ($12-25), and H. siariae ($12-25). All of them are native to the Philippines.

Species that command the highest prices are: 1) new species owing to its rarity, 2) those that are difficult to grow (species found in high elevation and with thin foliage), 3) variegated species (marginate or internal on the leaves), and 4) those superior and novel hybridized selections.

According to Siar, most of Philippine Hoyas are currently in the hands of foreign collectors, hobbyists, and plant enthusiasts. She emphasized the need to recollect, preserve, study, and utilize germplasm of these precious plants.

She suggested important things to be done in order that the country would be able to capitalize on the popularity of Philippine Hoyas: 1) intensive studies in the possible medicinal qualities of the Hoyas since very little study has been made on this area of research; 2) possibility of exports to Scandinavian countries since their quarantine policies are less strict, unlike in the United States; 3) start developing new hybrids of Hoyas with more vigor, better form, disease-resistant, and compact growth since they command the highest price in the world trade; 4) opportunity for growers to grow variegations, with great color changes, leaf shape, and texture through selective cuttings; and 5) discover new species of Hoyas since they command high price. end

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For more information please contact D. Monina V. Siar at the Institute of Plant Breeding (IPB), University of the Philippines, Los Baņos, College, Laguna 4030 through telephone numbers: (049) 536-8750 or e-mail her at: moninasiar@yahoo.com

Sources:
 
 
    Copyright Š 2002 Bureau of Agricultural Research