Rhododendron viriosum hybrids

flowers of Rhododendron 'Festive Bells'
Rhododendron ‘Festive Bells’

Rhododendron ‘Festive Bells’ is currently flowering in my shade house, so this seems like a good time for a quick post on Rhododendron viriosum hybrids.

R. viriosum is a vireya, a tropical rhododendron, and is one of only two Rhododendron species native to Australia. It has red, bell shaped flowers and is noted for its phenotypic dominance and the vigor that it imparts to hybrids. Hybrids with R. viriosum as a parent almost invariably have bell shaped flowers in some shade of red, and they are usually strong growers. Appropriately, the species name virosum is derived from the same root as the English word “virile”. The species is difficult to locate in the United States, but I am currently growing two first-generation hybrids and have previously grown a third.

Rhododendron ‘Festive Bells’, shown above, is my favorite of the three. My plant, purchased a year ago, is currently blooming for the first time, and the flowers are absolutely amazing. They are some of the best flowers that I have ever seen on a rhododendron, and perhaps on any plant. The color is a pure, intense fire engine red and the flowers have an incredible waxy texture that makes them look as though they are made of plastic. Like many vireyas, R. ‘Festive Bells’ is somewhat lanky with long internodes, but flowers are nicely in-proportion with the plant size. R. ‘Festive Bells’ has R. viriosum as the seed parent, but the pollen parent is unknown.

Flowers of Bovees V97
Rhododendron viriosum x christianae (Bovees V97)

Bovees V97 is an unregistered clone of R. viriosum x R. christianae bred by E. White Smith, former owner the Bovees Nursery in Portland, Oregon. Bovees was for many years the preeminent source of vireya plants in the United States. It closed a few years ago, so I was happy to find this hybrid still offered for sale by Pacific Island Nursery in Hawaii. Genes from R. christianae have imparted orange tones and a more horizontal stance to the flowers, but the plant still has the vigor expected of an R. viriosum hybrid.

flowers of Rhododendron 'Little Maria'
Rhododendron ‘Little Maria’

Rhododendron ‘Little Maria’ was a beautiful little plant that grew in my collection for about five years. The cross is R. viriosum x (viriosum x gracilentum). R. gracilentum is a miniature, cool-growing species from the mountains of New Guinea at altitudes of 2000-2745 m above sea level [1]. Despite the double dose of R. viriosum in the ancestry of R. ‘Little Maria’, R. gracilentum is dominant for plant size. A large specimen of ‘Little Maria’ can fit in a 4″ pot, and both leaves and flowers are about half the size of those of R. ‘Festive Bells’ or V97. Unfortunately, R. gracilentum also seems to be dominant for heat tolerance (or lack thereof). Plants purchased from Bovees died very quickly, but I had better luck with cuttings that I rooted in North Carolina. Anecdotally, I have noticed similar results with other vireyas. When vireya plants in my collection die, it often seems to be because the root system has failed catastrophically in the heat. For some reason, roots that have grown in North Carolina seem tougher–perhaps they have different fungal symbiotes or are better adapted to my potting mix.

Eventually, all of my Rhododendron ‘Little Maria’ cuttings died in the summer heat, and I have been unable to replace them. I am hopeful that V97 will do better in our climate, because R. christianae is from more moderate altitudes of 600-1525 m [1]. Since the other parent of ‘Festive Bells’ is unknown, I will just have to hope for the best, but I have already rooted a cutting as insurance.

Reference

1. Argent, G. (2015) Rhododendrons of subgenus Vireya, 2nd edition. Royal Botanic Garden, Edinburgh.

A modern vireya hybrid

Photo of a vireya rhododendron hybrid
Rhododendron praetervisum x ‘Doctor Hermann Sleumer’

As a complement to Rhododendron ‘Princess Alexandra’, the Victorian vireya that I wrote about in June, here is a more recent vireya hybrid. This plant is Rhododendron praetervisum x ‘Doctor Hermann Sleumer’, so its parentage is R. praetervisum x (konori var phaeopeplum x zoelleri). R. zoelleri has been known since the 1890s, but the type specimen of R. konori var. phaeopeplum was collected in 1939, and the type of R. praetervisum in 1965 [1]. The cross was made by Richard Currie in his New Zealand garden, presumably in the late 1970s or 1980s. One plant of this cross was registered as Rhododendron ‘Cheeky’ but I am not certain if my plant is a division of that cultivar or a sibling.

I previously grew a plant of R. praetervisum, but it never thrived, flowered infrequently, and died after about five years. I’m hopeful that this plant will exhibit hybrid vigor and, perhaps, inherit heat tolerance from R. zoelleri (native altitude range sea level-2000 m [1]). I purchased it in April, and it grew well in my shade house during the summer and has already flowered twice.

Incidentally, Hermann Sleumer was a botanist at the Rijksherbarium in Leiden who described hundreds of new vireya Rhododendron species in the 1950s and 60s, making him one of the most important names in the modern era of vireya cultivation. Both R. praetervisum and R. konori var phaeopeplum (as R. phaeopeplum) were described by Dr Sleumer.

Reference

1. Argent, G. (2015) Rhododendrons of subgenus Vireya, 2nd edition. Royal Botanic Garden, Edinburgh.

Rhododendron ‘Princess Alexandra’

Rhodo_Princess-Alexandra1

Rhododendron ‘Princess Alexandra’ is a vireya (tropical rhododendron) cultivar, the result of a backcross between the very first vireya hybrid, Rhododendron ‘Princess Royal’ (R. jasminiflorum x R. javanicum), and its parent R. jasminiflorum. It was registered by the famous nursery of J. Veitch & Sons in 1865, from which we can deduce that it was named in honor of Princess Alexandra of Denmark who had married Prince Albert Edward, the future King Edward VII, two years earlier.

Some plants remain consistently popular, while others go in and out of fashion. Vireyas definitely fall in the latter category. R. jasminiflorum flowered in England for the first time in 1849, and over the next fifty years or so, several hundred vireya hybrids were registered, mostly by the Veitch nurseries. Along with orchids and other tropical plants, vireyas graced the conservatories of the Victorian upper class, but their popularity was eventually eclipsed by hardier Rhododendron species which didn’t need an expensive heated greenhouse. It wasn’t until the second half of the twentieth century that an influx of newly discovered species made vireyas and their hybridization popular again. This second wave of cultivation occurred in places where vireyas could be grown outside–New Zealand, Australia, coastal California, Hawaii–and hybridizers focused on species from the mountains of Malesia (the biogeographic region encompassing Peninsular Malaysia, the Malay Archipelago, and New Guinea) that thrived in cool, but not freezing, weather.

In the the years between the first and second periods of vireya popularity, two world wars and a great depression wiped out many of the old collections of tropical plants, and fewer than ten of the Victorian hybrids survive today. I find it amazing that the R. ‘Princess Alexandra’ in my greenhouse is essentially the same plant that grew in the Veitch nurseries. It has been propagated by cuttings and traded among enthusiasts for more than 150 years.

I love to grow vireyas, but unfortunately most vireyas don’t love North Carolina. Although vireyas come from the tropics, most species grow at high altitude, up to and even above the tree line. The montane species–and hybrids dominated by those species–are weakened by our long, hot summers and tend to die suddenly after a few years. I have the best long-term success with the relatively few species that grow naturally a lower altitudes, and it is exactly those species, plants like R. jasminiflorum and R. javanicum, that are the parents of the Veitch hybrids. I’d love to grow more of the old survivors, if only I could find them.

So, if anyone knows where I can obtain cuttings of Rhododendron ‘Ne Plus Ultra’ or R. ‘Triumphans’ in the United States, please let me know.

Rhodo_Princess-Alexandra2

Six on Saturday #25, April 14, 2018

Spring has really gathered steam over the past week, and for the first time in a couple of months, I had to select from among a wide array of flowers for this Six on Saturday.

This week, I’ll start in the greenhouse and then move outside.

1.  Phalaenopsis mannii

Phal_mannii

The range of this small Phalaenopsis species extends from Assam to Vietnam and southern China.  In common with some other Phal species, you should never cut the inflorescences when the spring/summer flowering season is finished.  The old inflorescences will remain green through the winter and will produce new flower buds the next year.  At the same time, new inflorescences will sprout, so as the plant gets older you’ll have more and more flowers each year.

2.  Vireya hybrids (two for one)

Vireyas are a group of Rhododendron species from the old-world tropics, with the greatest diversity New Guinea, Borneo, Sulawesi, Sumatra, and the Philippines.  The majority of species are from high elevation, so they prefer mild temperatures and do not appreciate the warm summer nights in North Carolina.  In the USA, most vireya growers are on the west coast and Hawaii.

I have had long-term success with a few heat-tolerant vireyas whose ancestors come from lower elevations They do not tolerate frost, so in North Carolina they are definitely greenhouse plants.  I’ve been growing these two plants since 2004.

vireya2
Rhododendron jasminiflorum x (viriosum x jasminiflorum).  The pink color is a mix of the white R. jasminiflorum and red R. viriosum, but the long, tubular flower shape is all R. jasminiflorum.  This plant came from the late Bill Moyles, a well known vireya grower and hybridizer from Oakland, CA.

vireya1
This  complex hybrid with peachy flowers is another Bill Moyles cross. It is Rhododendron (Felinda x (aurigeranum x Dr. Hermann Sleumer)) x javanicum.   R. Felinda is ((phaeopeplum x viriosum) x leucogigas), and R. Dr. Hermann Sleumer is (phaeopeplum x zoelleri).

3. Ornithogalum dubium

ornithogalum-dubium

Ornithogalum dubium is commonly sold by supermarkets and hardware stores as a throw-away flowering plant in late winter.  Most people will probably treat them like cut flowers and toss the pot when the foliage starts to yellow.  To keep the plants for another year, store the dormant bulbs dry and warm (or even hot) over the summer.  Occasionally, bulbs will fail to sprout in autumn.  As long as they remain firm, give them occasional water through the winter and then another hot dry summer.  Often, they will sprout after the second dormancy.  I have maintained these for five years, so there’s definitely no need to buy a new pot full every year.

And now, outside for the remaining three plants this week…

4.  Tulipa clusiana var. chrysantha

clusiana-chrysantha1

Tulipa clusiana is reputed to be the best perennial tulip for the southeast.  I first saw them blooming in Coker Arboretum at the University of North Carolina and was thrilled to find that they are very inexpensive from internet bulb vendors.

T. clusiana var. chrysantha flowers open in mid-morning and close back into tight buds in late afternoon.  Although they have been flowering all week, I have seen only the orange buds when leaving the house and returning from work.  Today was the first time I saw the bright yellow open flowers.

clusiana-chrysantha2

5.  Saruma henryi 

IMG_4929 crop

The fuzzy stems of Saruma henryi are just starting to emerge from the mulch, and the first flower is still wrinkled.  S. henryi is related to Asarum, hence its genus name.   Saruma is an anagram of Asarum.  Those crazy botanists…

6.  Scilla peruviana

Scilla-peruviana

Despite the name, Scilla peruviana is from the Mediterranean–Portugal, Spain, and southern Italy–not South America.  The large bulbs produce their leaves in autumn, remain green all winter, and flower in spring.  When I planted the bulbs last autumn, I wasn’t sure if they would survive outside, but they tolerated 3.2 F (-16 C) with only minor damage to the leaf tips.

To see what’s growing in gardens all around the world, head to The Propagator for his Six on Saturday and links to those of other garden bloggers.