Paphiopedilum Johanna Burkhardt


I have previously written about two fine old primary hybrids made with Paphiopedilum rothschildianum: the Victorian P. Lady Isobel and P. Saint Swithin. Here is a modern one, and it may well be the best.

Paphiopedilum Johanna Burkhardt is P. rothschildianum x P. adductum, and it was registered in 1994. My plant was made using P. adductum var. anitum as the pollen parent, and the results are spectacular. P. rothschildianum has contributed flower size, number, and overall form, while genes from the very dark P. adductum var. anitum have produced a dorsal sepal, petals, and pouch with dark reddish-brown markings on a yellow background. P. adductum var. anitum has also reduced the overall size of the plant, without affecting flower size; this plant has about half the leaf-span of my other P. rothschildianum hybrids, but its flowers are just as large, if not larger. A Google search for this grex will turn up pictures of better clones, many of them awarded, with huge, muscular-looking flowers and dorsal sepals that are almost black.

P. adductum var. anitum is sometimes considered a separate species, P. anitum, in which case this hybrid would be P. Wössner Black Wings (P. rothschildianum x P. anitum). From a horticultural point of view, there’s something to be said for distinguishing the dark plants made with P. adductum var anitum from those made with lighter colored P. adductum clones. However, the International Orchid Register lists P. Wössner Black Wings as a later synonym of P. Johanna Burkhardt, and both the Kew World Checklist of Selected Plant Families and a recent checklist of the genus Paphiopedilum (Koopowitz, H., 2018, Orchid Digest 82: 178-235) consider P. anitum to be a synonym of P. adductum.

Eight hybrids using P. Johanna Burkhardt as a parent have been registered, but none of the photos I have seen suggest that they are any better than–or even as good as–their parent. I’d go so far as to say that in this group of orchids, the primary hybrids are almost always better than complex hybrids. After more than 120 years, P. Lady Isobel and P. Saint Swithin are still well worth growing, and I suspect that the same will be true of P. Johanna Burkhardt in another century.

Six on Saturday #64 (March 13, 2021)

What a difference a few weeks makes. This week has been brightly sunny, and the high temperature was about 80 F (26.5 C). The spring bulbs and hellebores are nearing their peak, the garden is perfumed by Edgeworthia chrysantha, Lonicera fragrantissima, and Osmanthus fragrans, and the fence lizards are skittering about in the leaf litter.

1. Cypripedium formosanum (Formosan lady’s slipper orchid)


After three years, my C. formosanum is still going strong. I think this year’s flower is the nicest so far. The plant is in an 8-inch diameter pot with a mix of composted wood chips, peat, and stalite. It lives outside under shade cloth in summer and spends the winter on the floor of the greenhouse, near the cold draught from the imperfectly sealed swamp cooler.

2. Hellebore flowers

Hellebore flowers floating in a dish

The pure white flowers at center left and 5 o’clock are Helleborus niger. The large reddish flower at 10 o’clock is Helleborus x iburgensis ‘Anna’s Red’. The others are all seed-grown Helleborus x hybridus.

3. Narcissus ‘Odoratus’


This is a dwarf tazetta Narcissus. According to various web sources, it was discovered somewhere on the Isles of Scilly by the horticulturalist Alec Gray. To my nose it is only faintly fragrant, despite the cultivar name.

4. Narcissus x odorus (Campernelle)


Narcissus x odorus is a centuries-old hybrid of N. jonquilla x N. pseudonarcissus. It has been grown in North Carolina since the colonial period. The blue-green foliage in the foreground is Tulipa clusiana var. chrysantha (see photo 2 here).

5. Cackleberries


The tiny dinosaurs have started laying, and between the five of them, we are averaging about four eggs a day! The very pale blue-gray eggses are from Hühnchen and Kuritsa. Dark brown with darker speckles is from Pollo, large brown from Kylling, and small, light brown from Frango.

6. Vegetable seedlings

A picture of Cypripedium formosanum

I handle the ornamental perennials, but vegetables are my wife’s domain–she’ll have more than a dozen different varieties of Asian greens and kale, along with tomatoes, malabar spinach, spigariello, lettuce, and a few annual flowers ready to plant out next month. The glow from her new LED grow lights makes our house look like something out of “The Amityville Horror” at night, but the seedlings seem to love it.

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.

Lord Rothschild and Saint Swithin

Mature Paphiopedilum rothschildianum can have 4-6 flowers on an inflorescence, so this plant with three flowers is still just a baby.

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 [1]. 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.

The hook-shaped staminode of P. rothschildianum is covered with glandular hairs. It has been suggested that the hairs mimic an aphid colony to attract the predatory hoverflies which pollinate the flower [2].

Paphiopedilum Saint Swithin

Paphiopedilum saint Swithin inflorescence with four flowers
Paphiopedilum St Swithin, first bloom seedling with four flowers on a single growth.

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.


  1. 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 Conservation 24:1641–1656
  2. Atwood, J.T. (1985). Pollination of Paphiopedilum rothschildianum: brood-site deception. National Geographic Research 1: 247-254.

Darwin’s Orchid

A seedling of Angraecum sesquipedale flowering for the first time.

“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.”

Entrance to the nectary. Darwin recognized that if a moth is forced to stretch for nectar, its proboscis will be more likely to slide into the notch in the column and the moth’s head will come in contact with the pollinia hidden under the round anther cap.

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 Outreach 3: 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 Acta 110: 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:

crab spider attacking a butterfly
A crab spider in my garden demonstrating that it can capture butterflies and moths considerably larger than its own body.

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.

Angraecum sesquipedale-spring blooming form photgraphed in about 2005
A larger plant of the spring-blooming form of Angraecum sesquipedale that I was growing about fifteen years ago.


Loooooong petals

inflorescence of Paphiopedilum Michael Koopowitz
Seedling of Paphiopedilum Michael Koopowitz flowering for the first time. Its petals are at least 40 cm long.

Paphiopedilum Michael Koopowitz is a primary hybrid of Paphiopedilum philippinense and Paphiopedilum sanderianum, the two species in the genus with the longest petals. P. philippinense var. 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.

Another view. The parents of this plant are P. philippinense ‘Super Twister’ and P. sanderianum ‘Lady in Red’