JARS v56n2 - There is a Vireya Rhododendron For Almost Any Hawai'i Garden

There is a Vireya Rhododendron For Almost Any Hawai'i Garden
Sherla Bertelmann and Richard Marques
Kea'au, Hawai'i

It was in 1997 that we attended our first meeting of the soon to be Hawai'i Chapter of the American Rhododendron Society. At the front of the room, placed on a table, were flowers of the most brilliant hues and in various shapes and sizes. We stared in awe, little knowing that our lives were about to change.

Future chapter meetings were held at different member's gardens where vireyas (pronounced vie-RAY-ya) could be seen growing in all their glory. One member was located in Volcano Village at 4,000-foot (1200 m) elevation, another located on the Hamakua Coast along the sea cliffs at about 100-foot (30 m) elevation. Here was the proof of the pudding that not only could vireyas grow in Hawai'i but could grow at various elevations with vigor, producing masses of blooms.

At each meeting members would share their experiences, and at the end of each meeting we took home vireya cuttings in hopes of getting them rooted. In the last four years we have learned not only how to root vireyas but also just what it takes to keep them alive, healthy and repeatedly blooming. As our expertise grew, so did our membership. The Hawai'i Chapter ARS now has more than 100 members worldwide.

Personally we not only became involved with the chapter but so loved the plant that we chose to specialize in growing and selling vireyas from our nursery located in Kea'au on the Big Island of Hawai'i. Their diversity and adaptability continues to amaze us as we see the continuing flow of new hybrids. It is our goal to dispel any fears about growing vireyas.

Vireyas are rhododendrons - semi-tropical rhododendrons. They grow mostly in the mountainous regions of Malesia centered in and around the equatorial zone including Indonesia, the Philippines, Malaysia, Borneo and Papua New Guinea. Of the 850 or so species that make up the genus Rhododendron , almost 300 are classified as vireyas (section Vireya ).

In their homelands, vireyas can be found growing as epiphytes in the moss-encrusted lofts of tree branches, on rocks, or just growing as terrestrials, on the ground. They grow on the edges of forests and in open grasslands, seeking light. They are often the first plants to colonize areas where the original vegetation has been destroyed.

Vireyas come in a variety of shapes and sizes ranging from dwarf mats at high altitudes to all sizes of shrubs, and even trees. Some have foliage that could be mistaken for pine needles; some have huge leaf blades a foot long with flowers to match. Their flowers are often fragrant and are the most colorful of all rhododendrons. Vibrant yellows and reds are common. Flower shapes vary from small, open cups to spidery clusters of long tubes.

While species are grown in cultivation, they require more specific environmental conditions than the hybrids, which are more vigorous and adaptable. On the Big Island, vireya hybrids exist in gardens from 4,000-foot (1200 m) elevation down to sea level on the Hamakua Coast, and in Waimea, Hilo and Kona. Though there may be slight differences in care required due to each person's micro-climate, there are some standards concerning the cultural care of vireyas that must be followed. It helps to think of them as orchids, with similar needs such as drainage and good air circulation.

Vireyas have very fine surface roots, as opposed to a tap root. Understanding this is important. It is these fine surface roots that dictate how to plant and care for them.

The most important factor that cannot be stressed enough is excellent drainage. It is not how much water is received that is important but rather how quickly the water drains. Vireyas do not like soggy feet. In such conditions they can develop root rot. They must be grown in a highly aerated planting mix. If you are growing the vireyas in pots, use a medium like coconut chunks with perlite, orchid bark with perlite or cinder with composted material. Vireyas, like orchids, prefer to be more potbound than over potted. When stepping up your plant, look for a pot that is wider rather than deeper to accommodate their spreading surface roots. There are some wonderful bulb pans available.

The second factor is shallow planting. Raised beds or mound plantings work the best for outdoor plantings, but whether in the ground or in a pot plant your vireya with the top of the root ball at or above soil level. Use loose, well draining media such as those mentioned above. Because vireya roots run close to the surface, they can heat up from the sun. Covering with several inches of coarse mulch will keep them cool.

The third factor is light. Bright light helps to set buds as well as to shorten stem internodes. Though vireyas love light, dappled light is recommended especially during our peak summer heat. Planting your vireyas under hapu'u (tree ferns), near other plantings or on the north or east side of your house will give some shade. This will help prevent leaf burn and faded out flowers. Leaf burn will not affect future growth or flower buds but can be unsightly. Though there are varieties that will take full sun, they do equally well under dappled light.

Too much shade may produce a leggy plant and not many flower buds. If you suspect this to be happening, move the plant to a brighter place. Allow a potted plant to adjust over time rather than moving it abruptly from shade to direct sun. In the ground, vireyas can be moved with little adverse reaction from transplanting.

Water as needed, allowing the vireya to dry out between waterings. Remember, vireyas don't mind water but do mind soggy feet. If your vireya is in a pot and you find the plant wilting daily, it may be time to step up your plant. A quick check of the root ball will tell you whether it is time or not. Again, remember not to over-pot and try to use a pot that is wider rather than deeper. (One member of the society grows his vireya in pots under hard cover with his orchids and waters once every six days.) For vireyas planted in the ground, a good watering every four to five days should be sufficient, depending upon your microclimate.

Maintenance
Pinching off new growth promotes more branching. Look for the young, tender new leaves and "pinch" them off. For larger plants, a good pruning will also help to induce new growth. Cut just above the leaf growth on a stem. The new shoots will come from just above the remaining leaves.

Deheading the seedpods will also encourage more branching and, thus, more flowers. Deheading is the removal of the seedpods left after the flower drops. Usually just a twist will remove them. This will put the energy back into new growth and bud development rather than into seed production.

Fertilizing should be very light. Too much fertilizer can kill your plant. A slow release fertilizer with trace elements such as Nutricote® 180* applied twice a year is enough. Foliar sprays such as MiracleGro®** are fine but use them at about quarter strength.

Pests and Problems
Root rot is the number one problem caused by poor drainage or planting too deep. The sign to look for is drooping leaves giving the appearance of needing water. If you look at the roots you will probably find brown roots rather than the white/cream colored roots on healthy plants, and sometimes there is an odor. There is not much you can do other than take as many cuttings of your plant as you can to start new plants. Prevention is the best cure: good drainage, an aerated media and shallow planting.

Lacewing insects can be a problem These are the same ones that attack azaleas leaving silver spots covering the leaves. Lacewings are considered a soft-bodied insect, like aphids or mealy bugs. Insecticidal soap will take care of the problem.

On the Big Island, we occasionally find borers in plants grown outside. A portion of a stem will dry up. A small hole in the stem will be at the point mid-way up the stem where the browning starts. Cut below that point and discard. (We don't know if this is a problem in other areas of Hawai'i. It is not a big concern here, rather more of a random thing that sometimes happens.)

Red spots can form on the leaves usually after the plant has undergone some type of stress, such as a drought. This is normal and won't affect the future growth or flowering of the plant.

Propagation
Vireyas can be easily rooted from cuttings. The most important thing is patience. Place a cutting in a loose medium out of direct sunlight. Keep it moist by daily misting and do not disturb it. Many a vireya were lost because of impatience. This is one of the first things we learned: "Do not give in to the urge to check for new roots". Some vireyas depending on the variety, can take as long as a year to root, though the average time is closer to three months. If the cutting takes, it will hold its leaves and you will see new growth coming from the top. If all the leaves fall off before the new growth, more than likely that cutting will not make it.

Vireyas can also be grown from seed. A single seed pod can contain as many as several hundred seeds. The diversity from seeds can be large, and thus exciting. But it may take three to eight years, again depending on the variety, before flowering begins, whereas from cuttings that time is cut in half. More information on seed growing can be gotten from the Hawai'i Chapter, which took over the ARS vireya seed distribution program from Bill Moyles of California this year.

Viva Vireya!
In the past few years the number of vireya hybrids coming into the islands has greatly increased. One reason for this is the Hawai'i Chapter ARS. Last year more than 75 new varieties were brought in from Australia. Networking with others in California has also brought in new hybrids.

Hybridizers in places such as the United States, New Zealand, Australia and Germany continue to explore new crosses. Goals include plants with compact growth and large fragrant flowers and large red or perhaps blue flowers. Species only recently discovered are being used in breeding programs, promising many years of new and exciting things to come from the vireya world.

Whether in home gardens or in the landscape, the future of vireyas in Hawai'i looks very bright. Hawai'i has proved to be an ideal place for growing vireyas, especially outdoors.

* Nutricote® Type180. A slow release fertilizer that releases 80% of its nitrogen over a 180-day period. The chemical analysis of Nutricote® products varies. Nutricote® 13-13-13 is recommended for rhododendrons by the manufacturer.
** MiracleGrw®. MiracleGro® 30-10-10 is recommended for rhododendrons by the manufacturer.

Sherla Bertelmann (Ma) and Richard Marques (Pa) are the owners of Pacific Island Nursery, a mail-order nursery located in Kea'au on the Big Island of Hawai'i specializing in vireya rhododendrons. They also ship internationally. Their web site is www.pacificislandnursery.com . They are members of the Hawai'i Chapter of the American Rhododendron Society.