About a third of all rhododendron species are tropical vireya rhododendrons. Vireyas are tropical rhododendrons and have scales, hence they are often lumped with the lepidote rhododendrons. The scales on the underside of the leaves are star-shaped, disk-shaped or lobed. Another unique feature, vireyas have no blue pigments, so there are no mauve, blue, purple or violet vireyas. Also, vireyas never have spotted flowers. Vireyas do have seeds with "tails" or "wings" on each end, and idioblast cells (very large storage cells), neither of which occurs with other rhododendrons. For the purpose of this website, the vireyas will be treated separately since they are very different from other lepidotes.
First, vireyas do not look like other rhododendrons. They typically bloom twice a year and have waxy flowers. They are usually called vireyas not rhododendrons. Azaleas have a similar situation and are seldom called rhododendrons. Of course, both vireyas and azaleas are rhododendrons.
Second, vireyas do not grow where other rhododendrons grow. They grow more like orchids and grow where orchids grow. They are found in tropical areas where there is no frost. They are often epiphytes and are commonly grown in fast draining mixes used for orchids such as a mix of conifer bark mini-nuggets, pumice, and perlite.
Some vireya rhododendrons are terrestrial in grass lands, growing in moss areas on the soil, but most that grow in the rain forest are also epiphytes or are only epiphytes, growing on other plants in the rain forest with their roots growing on the bark (not parasitically). Some even grow as lithophytes, meaning they grow on rock surfaces. Usually the rock or bark the vireya is growing on is mossy and the moss seams to provide the correct environment for the roots. This is especially true for those found in the tropical and subtropical regions of the Malay Peninsula, Sumatra, Java, the Philippines, the Solomon Islands, and Papua New Guinea. Almost half of the 319 vireya rhododendron species grow in Papua New Guinea, which is just south of the equator.
Almost all species of rhododendron grow on the edge of the forest where there is lots of light. What is different about vireyas is that if there is inadequate light they will end up as epiphytes on trees or tree ferns. Epiphytes usually enjoy a regular daily rain shower to moisten and sustain their relatively exposed roots. Whether terrestrial or epiphytic, Vireya roots, like all rhododendron roots, occupy the top surface of their planting medium forming wider mats as they grow older. Vireya, being largely epiphytic in nature, are tolerant of dry conditions once established.
Listing the Number of Vireya Species Found in Each Country (courtesy of vireya.net)
The Section Vireya, which has about 319 species, is found almost entirely in the mountains of Java and Sumatra, Borneo, the Philippine Islands and New Guinea . There is a single representative in Queensland, Australia. There is also a string of occurrences in the mountains of Malaysia and Thailand, connecting the high mountain archipelago with the mountainous region of SE Asia, which itself supports several Vireya species.
To successfully grow vireyas use 40% coarse perlite, 40% conifer bark mini-nuggets and 20% coarse peat moss for the potting mix. These plants do quite well when the roots become crowded; therefore, do not move up in pot size prematurely. Fertilize every four months with orchid fertilizer of liquid fish emulsion, together with chelated iron and Peters trace elements. Thorough watering is done once per week, allowing full drainage (not wet feet) in a dry apartment, but can be as infrequent as every ten days in a solarium or greenhouse full of plants and humidity. You must pinch and prune often to encourage a more compact growth in any vireya, especially when the plant is young. Pinch any solitary growing branch, even when the plant is only a few inches tall, until the vireya is three years old. Thereafter, pinch the new center growth as soon as the leaves start to develop and you know it is not a flower bud. The beginner can wait until the buds starts to grow either as leaves or flowers before attempting to differentiate between the two. Flower buds start at three to five years of age so after that the vireyas must be pruned ruthlessly. After all, Mother Nature frequently does this in the wild by freezing the top growth down to the ground.
Prune the leggy types; don't bother to pinch them. You see, lepidotes have dormant adventitious buds all over so they will sprout out after pruning. Just remember to prune evenly back to the lowest set of leaves. The apical dominance theory works here. If the plant is not pruned evenly, the topmost branch will be the one that grows at the expense of the lower branches. After the plant is four years old, you may cut back one-third of the plant each year.
Once a month, rose fungicide must be sprayed on all leaves until it runs off to combat powdery mildew. Mildew can build up tolerance; therefore, it is best to rotate between the mildew fungicides. Use 1 teaspoon per gallon of water, or 1 drop in 1/2 quart for hand sprayers. Always be alert for this disease and spray immediately if you see it.
Red spots are caused by a magnesium deficiency, and yellow leaves are from chlorosis or from a calcium deficiency. Use dolomite or gypsum, chelated iron or liquid iron. You may use ammonium sulfate (never the nitrate). Black leaf tips are from salt burn. Flush out the pot to cure it.
Directory of Contents for Henning's Rhododendron & Azalea Pages
•• Providing Information about the Genus Rhododendron since 1996 ••
Compatibility & Webmaster information: These pages were created in Adobe GoLive, Adobe DreamWeaver, and BBEdit by . They have been successfully tested on Mac and Windows computers, iPads, iPods, & iPhones and with various browsers including Camino, Chrome, Firefox, Internet Explorer, Netscape, OmniWeb, Opera, & Safari. They have also passed the internet standards of the W3C validator tests. They are now translated into over 60 other languages by Google. Please report any problems to . [Article in Kutztown Patriot about American Rhododendron Society Award.]