With its large, elegant flowers on an upright inflorescence Paphiopedilum rothschildianum is one of the most magnificent slipper orchid species, and it caused a sensation when introduced into cultivation in 1887. At first, its habitat was falsely said to be in New Guinea, probably to throw competing plant collectors off the trail, but although its true origin in Borneo was correctly reported in 1895, it was long considered extinct in the wild. The species was finally rediscovered 1959, when it became clear that wild populations are restricted to the vicinity of Mount Kinabalu. Of the three sites discovered, one has subsequently been completely destroyed by fire, leaving only two sites that are both within Kinabalu National Park . P. rothschildianum once had a reputation for being very slow growing and reluctant to bloom, but selective breeding has produced plants that grow at a reasonable speed and are not particularly difficult to flower. These artificially propagated plants are much to be preferred to wild plants that are sometimes still poached from the park.
P. rothschildianum was named in honor of Baron Ferdinand de Rothschild, a Victorian banker, politician, art collector, and orchid grower, making it a member of a select group of orchids named for the Rothschild family. The other members of that club–Eurychone rothschildiana, Ancistrochilus rothschildianus, Bulbophyllum rothschildianum, and Vanda Rothschildiana–are all fantastic plants.
Paphiopedilum Saint Swithin
Paphiopedilum Saint Swithin (P. philippinense x P. rothschildianum) was one of the earliest P. rothschildianum hybrids, and it is still one of the best. It was registered in 1900 by Thomas Statter, who three years earlier had also registered the famous cross of P. rothschildianum x P. stonei as P. Lady Isobel. Unfortunately, orchid hybrid registrations, unlike species descriptions, do not include an etymology section. While it was possible to deduce the identity of Lady Isobel (and correct a 120-year-old spelling error), it is unclear why Statter named a tropical slipper orchid after an Anglo-Saxon saint. Perhaps it first flowered on July 15, St Swithin’s Day, or perhaps Statter had some connection to one of the many schools and churches dedicated to St Swithin/Swithun.
What is clear is that P. St. Swithin is an excellent example of heterosis, the tendency of F1 hybrids to be more vigorous (larger, faster growing, more robust) than either parent. The flowers are somewhat variable, depending on the P. philippinense parent, but they are almost always good quality. My plant was bred using P. philippinense var roebelenii (see photo 1 here for an example), and that parentage is reflected in its long drooping petals. I have also seen plants with shorter petals held at a roughly 45-degree angle, which were presumably bred using P. philippinense plants with shorter petals.
Van der Ent, A., Van Vugt, R., and Wellinga, S.M. (2015) Ecology of Paphiopedilum rothschildianum at the type locality in Kinabalu Park (Sabah, Malaysia). Biodiversity and Conservation24:1641–1656
Atwood, J.T. (1985). Pollination of Paphiopedilum rothschildianum: brood-site deception. National Geographic Research 1: 247-254.
It’s Saturday, and ordinarily I’d think about a Six on Saturday post of plants in the garden or greenhouse. But the weather has been grotty for the past few days, with near constant cold rain mixed with occasional freezing rain, and although a few optimistic spring bulbs are sprouting, there’s hardly anything in bloom. The situation is a bit better in the greenhouse, but the dull gray weather isn’t the best for photographs, and honestly, it’s kind of cold and gloomy out there even with the propane heater.
So, I’m going to try something different. When not obsessing over orchid catalogs, I like to read science fiction novels, and although SF authors spend more time thinking about alien animals, they do occasionally pay attention to plants. Since it is Saturday, I have decided to limit this post to six novels–science fiction or fantasy–in which plants are significant to the plot, not just window dressing.
1. The Day of the Triffids, John Wyndham
John Wyndham’s novels and short stories were some of the first SF that I swiped from Dad’s bookshelf. The Chrysalids is definitely my favorite, but I also enjoyed Wyndham’s novel about motile carnivorous plants, The Day of the Triffids. If you have seen the 1962 movie, you’ll recall that the Triffids are alien in origin, arriving as spores in a meteor shower which blinds anyone who views it, leaving them easy prey. In the book, however, triffids predate the meteor shower and are widely farmed for their oil. The protagonist thinks they were probably bioengineered behind the iron curtain. The mass blinding event is unrelated to triffids and simply allows the plants to escape cultivation and act as a particularly nasty invasive species.
closest real-world analogue: Thankfully there aren’t any carnivorous plants that can kill humans with a venomous whip and then tear off gobbets of decomposing flesh. However, the sticky substance that allows the triffids to also trap insects reminds me of the flypaper traps of sundews (Drosera species).
2. The Integral Trees, Larry Niven
The eponymous integral trees grow in the Smoke Ring, a torus of breathable air orbiting a neutron star. Since they live in free fall, they don’t have massive roots, and instead have a tuft of foliage at each end of the trunk. Unequal stresses on each end pull the tufts in opposite directions and cause the tree to take on the shape of the integral symbol in calculus. The plot of the novel is kicked off by a feature of an integral tree’s life cycle that has unfortunate consequences for the human colonists who live in its tufts, but like some of Niven’s other novels (most notably Ringworld) this is a book where the setting is more interesting than the characters or plot.
closest real-world analogue: Bromeliads like Tillandsia species, I suppose. Tillandsias use their roots primarily as holdfasts and can be grown with no substrate at all. It’s not difficult to imagine one growing successfully in free fall.
3. Great North Road, Peter F. Hamilton
In Great North Road, artificial wormhole portals have allowed travel to a number of extra-solar planets. One of them, St. Libra, has a complex vegetable ecosystem and no animals at all. The novel is a typical Peter Hamilton doorstop with a huge cast and interleaved subplots that include a murder mystery and a war against an alien menace that looks like it will be a long defeat. All of the subplots involve the plants of St. Libra in one way or another.
closest real-world analogue: This is a spoiler, so I’ll transform it by rot13. Gur cynagf ner gur ovbybtvpny pbzcbaragf bs n cynargnel pbafpvbhfarff, onfvpnyyl gur Tnvn ulcbgurfvf eha nzhpx, fb gur pybfrfg erny-jbeyq nanybthr zvtug or sbhaq va gur erprag erfrnepu fubjvat gung gerrf bs qvssrerag fcrpvrf pna fjnc ahgevragf ivn zlpbeeuvmny pbaarpgvbaf orgjrra gurve ebbgf–n fbeg bs fybj pbzzhavpngvba.
4. The Serpent Sea, Martha Wells
Wells’s Raksura novels take place in a complex fantasy world inhabited by dozens of races, none of them human. The style is more swords-and-sorcery than epic fantasy, but the books also have an oddly science fictional quality; magic is treated like technology, and some of the characters are basically scientists. The main characters, the Raksura, are humanoids who can shape-shift into winged reptilian forms, but more interesting than that, they are eusocial. Although they are as intelligent as humans, they have biologically specialized castes rather like hive insects. Raksura colonies (courts) are mostly located in a rainforest region where they inhabit gigantic “mountain trees.” The Serpent Sea is the book in which mountain trees are introduced, and their biology drives the plot. But you should start reading with the first book in the series, The Cloud Roads. I can’t think of anything else quite like these novels.
It has been about twenty-five years since I first read World Without End. At the time, I had never read a fantasy novel inspired by Georgian/Victorian natural science and exploration, so World Without End and its sequel, Sea Without a Shore, scratched an itch I hadn’t known I had. The protagonist is a young empiricist (i.e. scientist) who bears a more than coincidental resemblance to a young Charles Darwin, and his voyage in the story is more than a little like the voyage of the Beagle or the expeditions of Captain Cook. The plot hinges on the mysterious characteristics of Spuriverna regis, a plant collected by a previous expedition to that world’s equivalent of Polynesia.
closest real-world analogue: any herb that has, or is purported to have, medicinal qualities. Spuriverna regis is a member of the Verbenaceae, as is the Lantana in my garden.
6. The Lord of the Rings, J.R.R. Tolkien
Of course The Lord of the Rings. Along with everything else, LotR is an extended celebration of Tolkien’s love for trees. It’s largely the detailed description of trees throughout the story that make it feel so real, so grounded in places that are entirely believable. There are the willows in the Old Forest, the hollies outside Moria, the mallorns in Lothlorien, and the sad, dead tree in Minas Tirith. And the ents, of course. At the other end of the size scale, there’s Athelas. The outcome of the war of the ring would have been quite different without that little herb’s medicinal qualities.
closest real-world analogue: With their smooth silvery bark and golden leaves that don’t fall until spring, I suspect that mallorns look a lot like fancier versions of beech trees.
If this weren’t supposed to be a Six on Saturday post, I could go on…and on. There’s Brian Aldiss’s Hothouse (aka The Long Afternoon of Earth). Ursula Vernon’s “The Tomato Thief” and “Sun, Moon, Dust” and Robert Silverberg’s “The Fangs of the Trees” are short stories, not novels, but otherwise fit the criteria. I’m tempted to mention Gerald Durrell’s satirical novel The Mockery Bird (so I will mention it). Its plot depends on the ecological relationships between a fictional bird, a fictional moth, and two fictional tree species, so I’ll consider it honorary science fiction (emphasis on the science).
What other novels and stories have very important plants?
“The Angraecum sesquipedale, of which the large six-rayed flowers, like stars formed of snow-white wax, have excited the admiration of travellers in Madagascar, must not be passed over. A green, whip-like nectary of astonishing length hangs down beneath the labellum. In several flowers sent to me by Mr. Bateman, I found the nectaries eleven and a half inches long, with only the lower inch and a half filled with nectar…in Madagascar there must be moths with proboscides capable of extension to a length between ten and eleven inches. This belief of mine has been ridiculed by some entomologists…”
— Charles Darwin, 1862, On the Various Contrivances by Which British and Foreign Orchids Are Fertilised by Insects, and On the Good Effects of Intercrossing.
Next Friday, February 12, is Charles Darwin’s birthday and not coincidentally is also Darwin Day, commemorating the great man’s myriad contributions to science. It is therefore appropriate that my Angraecum sesquipedale, commonly called Darwin’s orchid, is flowering this week. Darwin’s prediction of a sphinx moth with a prodigious proboscis was elaborated by Alfred Russell Wallace in 1867, but Darwin was not proven correct until 1903. The moth in question, a subspecies of the African Xanthopan morganii, was named X. morganii praedicta, and it was finally photographed in the act of pollinating an Angraecum in 1992.
In his discussion of the pollination mechanism of Angraecum sesquipedale, Darwin suggested that the plant would be most efficiently pollinated if a moth were forced to push against the flower as it stretched for nectar at the bottom of a nectary that was lightly longer than the moth’s proboscis. On the other hand, a moth would be more likely to obtain nectar if its proboscis were longer than the nectary:
“As certain moths of Madagascar became larger through natural selection…or as the proboscis alone was lengthened to obtain honey from the Angraecum and other deep tubular flowers, those individual plants of the Angraecum which had the longest nectaries, and which, consequently, compelled the moths to insert their proboscides up to the very base would be best fertilized. These plants would yield the most seed, and the seedlings would generally inherit long nectaries; and so it would be in successive generations of the plant and the moth. Thus it would appear that there has been a race in gaining length between the nectary of the Angraecum and the proboscis of certain moths.”
More recent research suggests that Darwin’s hypothesis was at least partially correct (for review, see Johnson S.D. and Anderson B., 2010, Coevolution Between Food-Rewarding Flowers and Their Pollinators, Evolution: Education and Outreach3: 32–39). Experimentally shortening the nectaries of other moth-pollinated flowers has confirmed Darwin’s hunch that they are most efficiently pollinated when the nectary is longer than the pollinator’s proboscis. It is also clear that there is an advantage in having a proboscis long enough to reach all of the nectar in deep flowers. However, flowers and pollinators may not be the only players in this evolutionary scenario. Darwin forgot predators.
When a sphinx moth with a very long proboscis feeds from a shorter nectary, the moth can maintain its distance from the flower and often engages in behavior called “swing-hovering”. This side-to-side movement is thought to be a response to predators, including spiders, which could trap a moth that is immobilized against a flower (Wasserthal L.T., 1997, Botanica Acta110: 343–59). Thus, predators might drive the evolution of proboscis length sufficient to allow swing-hovering while feeding, and proboscis length would drive the evolution of longer nectaries–which would then drive the evolution of an even longer proboscis, if the longer nectary made moths with shorter proboscises more vulnerable to predation. This predator hypothesis remains unproven in the absence of direct observation of spiders or other predators attacking sphinx moths on Angraecum flowers. However, there is this:
Quite apart from its fascinating position in the history of science, Angraecum sesquipedale is worth growing for its beautiful flowers and nocturnal fragrance. It isn’t a particularly difficult orchid to grow and will thrive if given Cattleya light and Phalaenopsis temperatures. Angraecoids notoriously dislike root disturbance, so it is best to use a potting mix that will last a long time. My current plant is in a mix of coarse Orchiata (Pinus radiata bark) and red lava rock, but I have also grown plants successfully in pure lava rock.
There seem to be two forms of the species with distinct flowering times, but it is not always obvious which form is being sold by a particular nursery. One form flowers in winter (late December-February) and the other in spring (often around Easter), but there are no significant morphological differences between the two forms. The winter-flowering form is sometimes in bloom for Christmas (hence its alternative common name, star of Bethlehem orchid), but I have more often seen the hybrid Angraecum Veitchii (A. sesquipedale x A. eburneum) flowering in December.
A. sesquipedale eventually becomes very large and ungainly, but seedlings start flowering relatively young and small. One way to avoid having your growing area swallowed up by a giant Angraecum is to replace your plant every five or six years. Sell the big plant, buy a small seedling, and pocket the price difference.
Paphiopedilum Michael Koopowitz is a primary hybrid of Paphiopedilum philippinense and Paphiopedilum sanderianum, the two species in the genus with the longest petals. P. philippinensevar. roebelenii has impressively long twisted petals (see photo 1 in Six on Saturday #55), but P. sanderianum is in a class by itself–its petals can be up to one meter long. The petals of P. Michael Koopowitz are intermediate between the two species, never approaching the length of P. sanderianum but still long enough to impress. Various fanciful explanations for the long petals of these slipper orchid species have been devised (ladders for ground-dwelling insects?!), but the current hypothesis (if I correctly remember a paper I can no longer locate) is that they make the flower more visible to flying insects. Insect compound eyes aren’t great at making high resolution images, but they readily detect the motion of petals twisting and drifting on the slightest breeze.
P. philippinense var. roebelenii was described in 1883 and P. sanderianum in 1886, but their hybrid was not registered until 1993, despite it being an obvious cross to make. The reason for this century-long delay is that P. sanderianum was lost in cultivation and believed extinct in the wild for most of the 20th century. It was rediscovered in northern Sarawak in 1978, and plants started trickling into cultivation in the 1980s. When I started growing orchids in the mid 1990s, seedlings of P. sanderianum and its hybrids sold for eye watering prices–far out of the reach of my student budget–but near blooming-size seedlings can now be readily obtained for less than $100. That’s still expensive for a plant, but on par with other multifloral slipper orchids.
This seedling P. Michael Koopowitz has grown much faster and flowered earlier than a seedling P. sanderianum that I purchased at the same time (hybrid vigor, yeah!). The inflorescence has three flowers with 40-cm petals, which isn’t bad for a single-growth plant. If all goes well for the next few years, I can hope for inflorescences with four or five flowers, and perhaps longer petals, when the plant has a few more growths.
2021 has started cloudy and damp, and since we have already had several hard freezes this winter, there isn’t much that’s growing outside apart from a some cold-weather greens in the vegetable garden. This Six on Saturday is, therefore, a grab bag of tropical plants from my greenhouse.
1. Paphiopedilum purpuratum
Paphiopedilum purpuratum is a small slipper orchid native to Hong Kong and adjacent mainland China. According to the IUCN Red List, it is critically endangered, with fewer than 250 individual plants surviving in the wild. Despite its rarity in the wild, it is well established in cultivation, and artificially propagated seedlings like this one are relatively inexpensive, making it even sadder that the wild plants are still collected for unscrupulous horticulturalists.
2. Hippeastrum puniceum ‘Ibitipoca’
Ibitipoca is a locality in Minas Gerais state, presumably where this clone of H. puniceum was originally collected.
3. Burbidgea schizocheila (golden brush ginger)
This very attractive dwarf ginger, endemic to Borneo, was once difficult to find in cultivation, but it is now being mass produced and shows up at local garden centers. I keep it outside in the summer, and it seems to flower mostly in winter without a prolonged dormant period.
Flowering for the first time after growing for five years in my greenhouse, this pretty little shrub is an epiphytic member of the blueberry family (Ericaceae) from Costa Rica, Panama, and northern Colombia. Like the Macleania species that I have previously discussed, its flowers are pollinated by hummingbirds. I really love the fantastic shapes and colors of the neotropical Ericaceae, and I hope that the Cavendishia will prove to be as floriferous as the Macleania, which flowers almost nonstop now that it has reached a decent size (see photo at top of this page).
5. Nepenthes tobaica
See Six on Saturday #12 for more information about Nepenthes pitcher plants. N. tobaica is a smallish species endemic to the region around Lake Toba on the island of Sumatra. My plant is still fairly young and only recently started producing fully mature pitchers.
6. Nepenthes rafflesiana
N. rafflesiana is a much larger species with a wider native range encompassing Borneo, Sumatra, Singapore, and penisular Malaysia. Compared to the clone that I previously photographed (see picture 5), this seed-grown plant has more squat lower pitchers, and I prefer its more evenly distributed red speckling and dark red petioles.
The Propagator is the host of Six on Saturday. Head over there to see his Six for this week and find links to the blogs of other participants.