Saturday, January 31, 2009

Touring the Latourias: An Overview of New Guinea Dendrobiums

Dendrobium is the second largest orchid genus after Bulbophyllum, with over a thousand species stretching from Australia to Northern India. The Latorias, aka the New Guinea Dendrobiums, are a small group of about 24 species, mainly from the warm, wet lowland areas of the island, although some species occur in the Solomon Islands, the Philippines and other nearby islands. They received their name from early orchid taxonomist C. Blume, who described D. spectabile in 1850 as a new genus Latourea, which is no longer recognized as separate from Dendrobium. I prefer the term “Latourias” to “New Guinea Dendrobiums” because, obviously, there are plenty of other Dendrobium species from New Guinea, many with completely different growth habits and cultural requirements, and not all of the Latourias are from New Guinea.

They are related to the Australian Dendrobiums of the Dendrocoryne section (speciosum, kingianum, etc.), but do not interbreed well with them, or with most other Dendrobiums either. They usually have long, club-shaped psuedobulbs with leaves on the top, and one or two flowering spikes coming out between the leaves. The flowers are usually white, yellow or green, often with purple spots. They’re not really huge, but they pack mass appeal when they reach mature size; multiple spikes per growth are not uncommon. Because of their remote habitats, very little was known about many Latourias until quite recently, when several species that had been ‘discovered’ early in the century and then pretty much forgotten were rediscovered and described in the 1970s and 80s. Hybridizing among the Latourias is likewise a recent phenomenon and still confined to just a couple of growers, mostly in Hawaii and Australia.

And yet there is every possibility that Latourias will join phal-type Dendrobiums as the most popular groups of the whole genus. Here’s why: they’re pretty easy to cultivate and flower, a bunch of them are minis or compact in habit, and in many cases their flowers can stay in perfect shape for 3 or more months! They flower quickly from seed, and are not seasonal in their flowering habit, so twice a year blooming is quite possible. Second generation hybrids are now coming onto the scene, promising even better flower colors and presentation on compact,fuss-free plants. You have to wonder why they remained little known for so long. One issue, as with so many new areas of breeding, is that not only were there few species in the hands of commercial growers, but the species and their breeding potential were not well known—and their relatively low fertility with other Dendrobiums made hybridizing look like a bad bet. Another is that Latouria species do have their bad points: their tall, narrow psuedobulbs make for ungainly plants that tip over if you breathe too hard on them, and the flowers can be hidden under the top leaves. These shortcomings are being addressed by both line-breeding of species and hybridizing.

As early as 1909, breeders were cross-ing Latourias with other Dendrobiums, but modern breeding within the section didn’t start until the 50’s and 60’s, with only a handful of hybrids registered by pioneering Australian grower Hermon Slade and a few others. Then in the late 80’s and 90’s, hybridizers began hitting their stride. Roy Tokunaga, the ‘R’ in H & R Orchids and one of the top Latouria breeders, relates that he and others saw the potential of Latourias as specimen plants, and started looking for species that could grow well in warmer climates and were not too tall and spindly, with good flower counts and presentation.

Latouria Species and Hybrids

Let’s look at the individual species and the magic they can make when crossed.

Possibly the most popular species for modern hybridizing is D. atroviolaceum; it’s compact, has nice purple-spotted white flowers that are large for the size of the plant, grows easily and can remain in bloom for up to six months. A pretty plant in its own right, it is the parent of a number of well-known hybrids such as Andree Millar, Roy Tokunaga and Wonder Nishii. Roy Tokunaga went one better and found a particularly dwarf clone of this species, ‘Pygmy’, and is remaking old
crosses with it to produce more compact plants, as well as new hybrids.

Next up is a charmer, D. aberrans, a true mini with pseudobulbs only a few inches tall. From the tips sprout little white flowers, blush pink around the labellum; they last and last and last—some claim up to 9 months! Its primary hybrids Maiden Charlotte and Mini Snowflake, are near-perfect windowsill orchids, being under 6” high, with clusters of long-lasting pretty white flowers that dance above the leaves.

D. alexanderae has red-spotted, twisted petals and a red-veined, dagger-shaped lip. It was once suspected of being a hybrid of D. spectabile, but is now considered a valid species. It is one of the taller-growing species in the section, but its size can be controlled in hybrids such as Green Elf and Spider Lily. It’s also fragrant, with a warm, honey-like scent that may be passed on to its progeny!

D. convolutum is the best known warm-growing, green-flowered species; many of the others come from high cloud forests and are more difficult to grow. It stands about a foot high, can flower any time during the year, and the flowers typically last 4-6 months. Growers use it to extend the flowering season and longevity in hybrids, although its green-to-chartreuse color combined with a wine-red lip is not everyone’s cup of tea. Combined with D. atroviolaceum it produces Andree Millar, and with D. aberrans makes Aussie’s Pixie. Other well-known hybrids include Gerald McCraith, Green Elf and Key Lime.

D. johnsoniae may be the most gorgeous Latouria: its large white flowers have upswept petals and tepals like wings, and red lines in the lip. These qualities have earned it awards as a straight species, unusual for a Latouria; it’s a parent of such distinguished hybrids as Roy Tokunaga and Stephen Batchelor. Its flowers also last for months and can occur in any season.

D. macrophyllum is very common in New Guinea and surrounding islands; its wide native habitat means it grows well in a variety of conditions. It’s one of the tallest, with psuedobulbs over 2 feet high. Like many Latourias, its flowers are covered with hairs on the backs of the petals and tepals. Flower count is up to 25 per spike, and its green-to-yellow flowers have a good size and shape. It was parent to many early Latouria hybrids, such as New Guinea, Nellie, and Caprice. It also appears to be more fertile with Dendrobiums from other sections, leading to interesting breeding possibilities.

D. rhodostictum is another compact gem similar to D. johnsoniae in size and looks: its white flowers have purple spots on the lip margins and are held above the foliage, they may have a light fragrance. Roy Tokunaga liked it so much he named one of its primary hybrids Nora Tokunaga after his wife; it’s also the other half of the popular Maiden Charlotte.

D. spectabile is weird. Really weird. Its flowers look like alien monsters, with bizarrely corkscrewed petals and sepals, yellow-green with heavy maroon spotting. It has a strong, sweet fragrance, rare in this group of species. It grows upwards of 2 feet tall, with spikes rising up above the leaves. As a parent, its twisted habit becomes more dramatic than grotesque in hybrids like Adara Nishii and Woodlawn. It appears to be growing more popular in the latest crop of hybrids, perhaps as growers look for something completely different.

One of the things that makes Latourias interesting to me is that their breeding potential has barely been tapped. The vast majority of registered hybrids are simple primary crosses, but more complex second generation hybrids are starting to show up. As with many orchids, a number of Latouria species show a lot of variation among seedlings, which growers like Roy Tokunaga are exploiting as they gain more experience with breeding and growing. Introducing parents from other sections has the potential to open up new colors, flower shapes and scents, much as the hot/cold Australian hybrids brought new shades and shapes to the tough, cool-growing Dendrocoryne species. The future is looking mighty bright for Latourias!

Culture

So, now how do you grow all these Latourias you’re about to buy? The basic conditions are warm, humid, and evenly moist: they don’t like daytime temperatures above the 80s or nighttime temps below the high 50s. They appreciate good humidity and air movement but tolerate dry air so long as they’re well watered. Watering well means keeping the medium moist but not soggy; new growths are particularly susceptible to rotting if water gets inside the unfolding leaves, so be very careful when watering from above. Mounted plants need a good soaking 3-5 times a week, depending on conditions. Weak fertilizing once every week or so is recommended. Latourias do best in bright but not full sun; I have found that Latourias will get leaf burn in a south-facing window without adequate shading at midday; a sunny east or west window should do fine. The smaller species and hybrids are particularly fine candidates for growing under lights. All need a fairly loose, well-draining mix, so that roots stay moist but are well aerated; baskets or clay pots are best. I’ve seen very dramatic mounted Latourias, but keeping them moist indoors is likely going to be a challenge. As always, small plants in small pots need more frequent watering then specimen-size orchids in large pots.

2 comments:

Anonymous said...

great advice on the latourias. have successfully grown d.aberrans indoors under lights in nyc. flowering now--it started spiking in july 2009. seems to tolerate the low humidity now in my place (it's been down to 29 percent!)

Jim Freeman said...

Glad you liked it!

FYI, both the American Orchid Society and Orchid Digest recently featured Latouria dendrobiums, the AOS in a special issue, and Orchid Digest in their Oct/Nov/Dec 10 issue. Check 'em out!