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

Darwin’s Orchid

Angraecum_sesquipedale
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.”

Angraecum-closeup
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.

Ang_sesquipedale2

Orchids and memory

Like any object that a person keeps for a long time, plants can accumulate individual, sentimental value well beyond the value that they would have to any other person. These two orchids, currently blooming in my greenhouse, remind me of orchid growers who were a significant influence on me when I was a novice.

Bulbophyllum rothschildianum ‘Red Chimney’ FCC/AOS

‘Red Chimney’ is a magnificent clone of a particularly attractive species. It originally received an Award of Merit (AM) from the American Orchid Society in 1976, and was subsequently upgraded to a First Class Certificate (FCC) in 1991. I obtained my division of ‘Red Chimney’ in 1998 from the late Jo Levy, a well known orchid grower and Bulbophyllum expert from Memphis, Tennessee. I never met her IRL, as they say, but we exchanged emails and traded plants back and forth. She always sent me many more plants than I sent her. Most of those plants have faded away, victims of pests, change in climate when I moved from Michigan to North Carolina, or neglect during those years when young children kept me busy, but my ‘Red Chimney’ is still going strong. I am happy to have been able to pass on more divisions of Jo’s plant to other orchid growers.

B. rothschildianum has an interesting history. As documented by Bill Thoms in his book Bulbophyllums: The Incomplete Guide from A to WHY?, it originally surfaced in 1892 in a box of “nearly dead orchid plants” shipped to England from the vicinity of Darjeeling. After that initial collection, it remained in cultivation but was lost in nature for almost a century before being rediscovered in 1991 in Nagaland. Based on the date that it was awarded, ‘Red Chimney’ is presumably descended from the original Victorian collection. Currently, the online Flora of China lists the species as being present in Yunnan, so perhaps it has (or had) a wider range in the southeastern foothills of the Himalayas.

Bulbophyllums are usually pollinated by flies, and the flowers’ scents include carrion, feces, urine, fungus, and in one eye-watering case, rotten salmon (any old-school molecular biologist who remembers using tetramethylethylenediamine to make polyacrylamide sequencing gels knows exactly what Bulbophyllum cupreum smells like). In comparison, growers of B. rothschildianum get off easy. The flowers smell like mushrooms, but the scent is faint and you don’t need to worry about driving away guests if you display the plant in your living room.

Cymbidium ensifolium ‘Iron Bone’

Cymbidium ensifolium has a long history of cultivation China and Japan where it is grown as much for its foliage as its flowers. The clone ‘Iron Bone’ is an alba form that lacks the narrow red stripes on sepals and petals and reddish spots on the labellum of wild-type clones. The flowers are understated, even for a species that will never be called spectacular, but my plant is special because it came from the collection of Jack Webster, who died in 2008. When I first moved to North Carolina, Jack was a fixture of the NC orchid world. He was a member of multiple local societies in central and eastern NC, many-time president and more-or-less permanent board member of the Triangle Orchid Society, tireless organizer of shows and exhibits, and expert on almost every aspect of orchid growing. No one has been able to replace him.

If I were growing this plant according to traditional Japanese aesthetics, I would have it in a tall, narrow ceramic pot carefully chosen to complement its elegant sword-like leaves. Alas, I am an uncouth Anglo-Saxon, so it is currently languishing in a black plastic nursery pot. Maybe I’ll move it into more attractive housing, as befits its cultural and personal history, this spring.

Six on Saturday #59 (August 1, 2020)

This week’s Six on Saturday includes a couple of native species, an unusual vegetable, a cute little bulb from South Africa, a classic Victorian hybrid, and a greenhouse orchid that is really very nasty.

1. Bulbophyllum phalaenopsis

Bulbophyllum-phalaenopsis

This is not an orchid for growing on your windowsill or decorating your table at a dinner party.  If you think that the flowers of Bulbophyllum phalaenopsis look a bit like rotting meat covered with yellowish maggots, I can assure you that they smell exactly the way they look.  B. phalaenopsis is pollinated by flies looking for a place to lay their eggs, but if the fly is fooled by the ersatz carrion, the maggots will starve.

2. Canna ‘Ehemannii’

canna-ehemannii

C. ‘Ehemannii’ is an old Victorian hybrid of C. iridiflora crossed with (probably) C. indica, and it has inherited its drooping inflorescence from C. iridiflora.  Several modern C. iridiflora hybrids, including Canna ‘Orange Crush’ failed to survive the winter in my garden, but this plant, which I received from Bittster of Sorta Like Suburbia fame, has survived two winters so far.  I’m glad, because I adore the intense magenta color that is so very different than any other canna in my garden.

3. Sabatia species

Sabatia

This pretty little native wildflower often shows up at the edge of my lawn (i.e. the patch of weeds and moss that survive being mowed).  I think it is Sabatia angularis (rosepink), a widespread annual, but I am not certain.

4. Eucomis vandermerwei

Eucomis-vandermerwei

E. vandermerwei, from South Africa, is one of the smallest of the pineapple lilies. Along with E. zambesiaca, it seems to be resistant to the wilting exhibited by many other Eucomis in hot sunlight, making it a good choice for a North Carolina garden.

5. Allium cernuum (nodding onion)

Allium-cernuum

The nodding onion has a very wide native range, spanning the United States from Atlantic to Pacific.  In North Carolina its distribution is spotty, and although it has been reported from this county, my plants were purchased from the North Carolina Botanical Garden.  Leaves and flowers are edible but strong tasting.  I prefer to eat garlic chives.

6. Melothria scabra (Mexican sour gherkin, cucamelon)

Melothria_scabra

First fruit from from a plant that we bought on a whim from a veggie seedling rack this spring.  The plant looks almost identical to the weedy Melothria pendula but its fruit are better tasting.  I could probably have left these to get a bit bigger, but then I’d risk losing them to the tree rats.

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.

Renanthera Jenny Wren

Renanthera_Jenny-Wren

‘Tis the season for Renanthera flowers.  My R. imschootiana is still blooming, and this week the buds on my R. Jenny Wren started to open.  Renanthera Jenny Wren is a complex hybrid whose ancestry incorporates R. storiei, R. philippinensis, R. monachica, and R. imschootiana.   The mix of lowland (R. philippinensis, R. monachica) and higher elevation species (R. imschootiana, R. storiei) has produced a fairly adaptable grex.  Although it has several doses of genes from the giant R. storiei, the other parent species are smaller, resulting in a more manageable plant. Flowers seem to be somewhat variable.  My plant has rich, red flowers with darker red spots, but here is a plant with red spots on an orange background, more reminiscent of R. monachica.

The cross was made by Carter and Holmes Orchids, but I requested, and was granted, permission to register the grex when I first bloomed it in 2004. I named it for my wife, Jennifer.