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.

Juanulloa mexicana

Juanulloa1

You really can’t go wrong with a hummingbird-pollinated plant. The little birds are attracted to bright colors–primarily red, but also orange, yellow, and magenta–and flowers adapted to hummingbird pollination generally have interesting tubular or bell-like shapes. The only downsides to the hummingbird pollination syndrome are that the flowers usually lack fragrance, and the plants are often not heat-tolerant; hummingbird-pollinated plants are often native to tropical cloud forests where hummingbirds are most diverse and flying insects relatively rare.

Juanulloa mexicana (syn. J. aurantiaca) is a semi-epiphytic shrub that has all the good qualities of a hummingbird-pollinated plant but also exhibits considerable heat and drought tolerance. The plant itself is rather messy–or “interesting” if we want to be charitable. It has long, poorly branched stems that presumably ramble through the branches of host plants or over rocks in its native habitat. The leaves are widely spaced, and adventitious roots can emerge from almost anywhere along the stems. The roots adhere tightly to any surface they come in contact with (greenhouse benches, other pots, the gravel floor of the greenhouse, etc), and once they become large and woody, they can sprout their own leafy stems. When the plant is grown in a pot, roots will creep over the edge and emerge from drainage holes. The thin leaves are subject to infestations of mealybugs and spider mites, and they drop in the autumn, leaving the plant a leafless tangle of stems and roots for much of the winter.

But when it blooms, I forget how inelegant the plant is. The tubular flowers, which grow on short inflorescences, generally near the end of a stem, are dark orange and nestle in a slightly lighter orange calyx. I generally see flowers during the summer, but the plant can also bloom in winter while leafless. My plant seems to be self-sterile; despite numerous visits from hummingbirds and several attempts at hand pollination, I have never obtained seed.

Fortunately, however, J. mexicana is very easy to propagate from stem or root cuttings. I have used moist sphagnum moss and commercial potting mix with equal success, and I suspect that cuttings would grow just fine in damp paper towels or gravel. Stem cuttings will flower more quickly, but root cuttings might give you a more interesting specimen. One of my plants, grown from a piece of root that invaded a neighboring pot, has produced an above-ground tuber which is currently about the size of a plum or very large hen’s egg. Lignotubers are not uncommon in epiphytic shrubs (e.g. epiphytic Ericaceae), and several species of the related genus Markea produce tubers that are often hollow and inhabited by ants. However, I have been unable to find any literature describing tuber growth in Juanulloa. I am unsure if this is normal (i.e. a lignotuber) or abnormal growth (i.e. a burl or something similar). If anyone has any insight, please let me know. I’d be particularly interested to know whether seedlings produce a similar tuber.

Juanulloa2
Tuber at the base of a Juanulloa mexicana plant grown from a small root cutting. Note the new leafy stem sprouting from the old root at lower right.
Juanulloa3
Another view of the tuber

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 style. 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 #57 (June 20, 2020)

Is it Saturday again?  Here are six plants that are currently flowering.

1. Amorpha canescens (leadplant)

Amorpha-canescens

This is a plant that rewards close inspection.  Its purple flowers with golden yellow stamens are gorgeous, but tiny.  A. canescens is native to the central United States, from Minnesota and North Dakota to Texas.  I grow it a sunny, dry location near our rosemary bush.

2. Canna ‘Lucifer’

Canna-Lucifer

The somewhat dull orange-red flowers of ‘Lucifer’ can’t hold a candle to Canna ‘Flaming Kabobs’, but ‘Lucifer is probably much better suited to small gardens.  It is a miniature, standing only 3 feet high with inflorescence (90-100 cm), less than half the height of ‘Flaming Kabobs’.  I am growing it in somewhat poor, dry soil, but it has proven to be a tough little plant and has slowly spread into a clump about four feet wide.

3.  Habranthus tubispathus var. texensis (Texas copperlily)

Habranthus -texensis

This is a rather nice weed.  Seed must have drifted from some potted bulbs, and now a little Habranthus is blooming right at the edge of our driveway.  H. tubispathus has a disjunct range in southern South America, Mexico, the Caribbean, and the gulf coast of the United States.  It seems likely that it was originally native to Argentina, Uruguay, and Paraguay, but was introduced to other areas by early Spanish explorers and settlers.

4. Lonicera sempervirens (coral honeysuckle)–again.

Lonicera-sempervirens

Although some selected cultivars of our native L. sempervirens flower on and off for much of the summer, this wild vine at the edge of my garden usually blooms only in April.  I suspect it has been induced to flower again by the unusually cool and wet weather we have been having.

5. Buddleja davidii (butterfly bush)

Buddleja-davidii

I’m keeping a watchful eye on this plant.  It volunteered in the garden and has the potential to become quite invasive in our climate, but so far I have not found any more seedlings.  I keep it around, despite its large size and ungainly branches, because butterflies adore the flowers.  Some years, it is completely smothered in several species of swallowtail butterflies, but this year there are hardly any around.  I wonder if the wet weather is to blame.

6.  Hydrangea macrophylla ‘Bailmer’ (Endless Summer Hydrangea)

Endless-Summer

I have shown this plant before, but it is blooming particularly well this year.  Gardeners generally think that blue flowers occur when H. macrophylla is grown in acidic soil and pink flowers in neutral or alkaline soil, but the situation is a bit more complex, depending on availability of aluminum ions and the amount of phosphate in the soil.  Having blue and pink flowers on the same plant, and even on the same branches, should probably tell me something about my soil chemistry, but I have no idea what.

The Propagator is the host of Six on Saturday.  Head over there to see his Six and find links to the blogs of other participants.

Six on Saturday #56 (May 23, 2020)

oxalis-articulata-2
Oxalis articulata

File under things that are counterintuitive:  the Raleigh/Durham, North Carolina area, which I perceive as being fairly sunny year-round,  receives more than twice the annual rainfall of notoriously damp London, England.  Part of the answer to this apparent conundrum is that London has more drizzly days (RDU has 109 days with some precipitation vs London’s 164).  Furthermore, we tend to have tropical-like afternoon thunderstorms during the summer, so many of those 109 rainy days are mostly sunny with thirty or forty minutes of heavy rain around the evening rush hour.

But sometimes we do have prolonged wet periods.  The freeze warning two weeks ago proved to be a false alarm, but this week has also been cooler than normal.  It was the cool of clouds and heavy rain, though, not the chill of dry Canadian air driven south.  Between Monday night and Friday morning, we received 6 inches (~15 cm) of rain.  The garden is looking particularly lush, but some plants are a bit floppy after growing like crazy for a week under heavy cloud cover.

Despite several of this week’s Six on Saturday originating in South America, all are garden plants that grow outside in the ground year round.  Most of these photos were taken last Saturday, before the heavy rain.  They’d look a lot more bedraggled if I photographed them today.

1. Cypella herbertii subsp. brevicristata

herbertii-brevicristata
Cypella herbertii subsp. brevicristata

Cypella herbertii is a small iris-relative from Argentina and Uruguay.  I have previously written about C. herbertii subsp. herbertii, and everything I wrote about culture applies to this subspecies, too.  Technically, the two subspecies are distinguished by the length of the stigma lobes, but the two forms that I grow also differ in their color:  my T. h. brevicristata has flowers of a clear yellow, while those of my T. h. herbertii are more orange.  This is the first year that my T. h. brevicristata has flowered, so it will be interesting to see if I get a mixture of colors among the volunteer seedlings in future years.

herbertii-herbertii
For comparison, here is Cypella herbertii subsp. herbertii

2. Hippeastrum x johnsonii (St. Joseph’s lily)

Hippeastrum-johnsonii

I featured this hybrid in my very first blog post.  At that time, I was growing it in my greenhouse, but I have since transplanted it to several places in the garden.  The best clump grows in full sun beside the bird bath, in soil that stays damp year round. H. x johnsonii,  a cross of H. reginae (southern Brazil) and H. vittatum (Peru), was the first artificial Hippeastrum hybrid. Its name commemorates Arthur Johnson, an English watchmaker and horticultural enthusiast who first made the cross at the end of the 18th century.  Surprisingly, given the origins of the parent species, H. x johnsonii is reputed to be among the most cold-hardy and vigorous of all Hippeastrum hybrids.

3. Clematis ‘Rooguchi’ (?)

rooguchi

The first flower on a Clematis that I planted last autumn.  I’m not entirely sure that it is correctly labeled.  The flower looks right, but Missouri Botanical Garden’s Plant Finder says that C. ‘Rooguchi’ is a non-vining hybrid lacking the twining petioles that help the vining varieties climb.  My plant definitely has twining petioles and is enthusiastically climbing some deer fencing stapled to the pergola.  Some websites agree with MoBot, while others say ‘Rooguchi’ is a climber like my plant.  Perhaps there are several different clones of the same cross all going under the same cultivar name?

4. Foundation plantings

Rosa_and_Phlomis

A two-for-one entry.  Along the south-facing foundation of our house, I planted a row of Rosa ‘Home Run’ and a clump of Phlomis fruticosa (Jerusalem sage) which is slowly spreading to surround the roses.  The Home Run rose is single-flowered (which I like) but lacks fragrance (which I do not).  Most importantly, though, it is very resistant to blights and mildews during hot, humid weather.

Home-run

P. fruticosa is marginally hardy here, so planting along the south foundation gives it sun in winter and protection from cold north and east winds.  Even so, it doesn’t flower very well and is sometimes damaged by snow and ice sliding off the roof. I do like the foliage, though, and the contrast with the glossy rose leaves.

Phlomis-fruticosa

5. Oxalis tetraphylla ‘Iron Cross’

Oxalis-tetraphylla-1

O. tetraphylla is from central Mexico and is one of the Oxalis species that grow from little corms.  I received it as a freebie in a bulb order five or six years ago and decide to chance growing it in the ground.  So far, it has been well-behaved in the garden, tolerating freezing temperatures and showing no tendency to spread and become a weed like some Oxalis.

Oxalis-tetraphylla-2

6. Oxalis articulata (syn. O. crassipes)

oxalis-articulata

I found this plant growing on our property when we first moved into our newly built house.  O. articulata is a South American species with a long history in cultivation, so I suspect that like the Gladiolus ‘Eno Orange’ it may have been planted by previous owners of the land and survived the intervening years when the property was left fallow.  I have since dug it up and distributed the knobbly little rhizomes to several places in my garden.  O. articulata can apparently become mildly invasive in some climates, but my plant seems to be sterile, at least in the absence of another clone, and shows no inclination to spread on its own.

The Propagator is the host of Six on Saturday.  Head over there to see his Six and find links to the blogs of other participants.