Rubiaceous Ant Plants (Six on Saturday #17, November 25, 2017)

After a couple of weeks absence, here’s another Six on Saturday.  As with previous posts on Pachypodium and Nepenthes, I’m focusing on a single group of greenhouse plants this week.

Myrmecodia platytyrea (Mossman Gorge form) overflowing a 5-inch pot

The epiphytic myrmecophytes (ant plants) of the coffee family, Rubiaceae, are surely some of the strangest plants that grow anywhere in the world.  Their overall appearance is often grotesque: gray or silver or brown blobs with thick, armored stems and sharp spines derived from modified roots.  They cling to tree trunks or hang upside down below horizontal branches, looking like aliens that have inexplicably settled in an Asian forest.  And to top all of that, their real strangeness is hidden inside.  Soon after a seedling ant plant germinates, the hypocotyl–the stem below the cotyledons–starts to swell into a tuber.  As the plant grows, tissue within the tuber dies in a genetically programmed manner, first forming a hollow space and then expanding into a series of tunnels and chambers.  The tunnels are connected to the outside by entrance holes around the base of the tuber, and the chambers are often aerated by pores.

All of this baroque development is for the benefit of symbiotic ant colonies who set up housekeeping in the artificial nest that the plant has grown.  Both insects and plant benefit from the relationship.  The ants get a secure home, and the plant is fed by the ants.  The ants live in smooth-walled chambers and deposit leftover fragments of insect prey and other waste in chambers with wart-like excrescences on the walls.  As the waste decomposes, the plant absorbs nitrogen through the warts.

Myrmecodia tuberosa cut to reveal interior chambers (a photo from my defunct ant plant website, ca. 1998)

 

Closeup of chambers.  Arrows indicate two warted chambers.  Smooth chambers can be seen at the center of the slice.

The natural range of the rubiaceous ant plants extends from Thailand to Australia and east as far as Fiji, but the greatest diversity is found on New Guinea.  In the mid-1990s, when I first became interested in ant plants, only about five species were in cultivation, and they were very hard to find.  With some effort (i.e. obsessive searching), I managed to connect with a few other like-minded growers via email and traded seed and seedlings with the curators of several botanical gardens.  These days, the plants are (somewhat) easier to obtain, and a wider range of genera and species are in cultivation thanks to the efforts of a handful of hobbyists and nursery owners from around the world.  Several nurseries in Europe and the U.S.A. sell seedlings, and plants are occasionally available on eBay.

So without further ado, here are six (on Saturday) ant plant species:

1.  Myrmecodia platytyrea (Mossman Gorge form)

The plant shown at the top of this post is a very vigorous Myrmecodia descended from material originally collected in northern Queensland.  Like most of the rubiaceous ant plants in cultivation, M. platytyrea has flowers that self-pollinate, so seedlings remain true to type over multiple generations.  The Mossman Gorge form of M. platytyrea produces long, sharp spines and very vigorous roots that often invade the pots of its neighbors.  Its leaves are narrower and more succulent than other cultivated M. platytyrea descended from plants collected in New Guinea.

The shield-like leaf bases on the stems of M. platytyrea are called clypeoli.  The spines bordering the clypeoli hide alveoli, pits in which the small white flowers develop and from which the orange fruit protrudes when ripe.

2.  Myrmecodia sp. “Pink Fruit”

This species has very strong sharp spines and pink fruit.  It is commonly cultivated by ant plant enthusiasts, but its origins are obscure.  Possibly, it is M. tuberosa ‘Papuana’ which grows in New Guinea and northern Australia.

3.  Myrmecodia tuberosa

This is the most variable and widespread Myrmecodia species, with a range extending from Malaysia to Australia.  The form shown here does not have strongly developed clypeoli, so you can easily see the elongated alveoli filled with papery bracts.

4.  Myrmephytum beccarii

Myrmephytum is a genus of five species found in the Philippines, Sulawesi, and western New Guinea.  M. beccarii is from the Philippines, and was introduced into cultivation in the U.S. around 2006.

5. Hydnophytum moseleyanum

H. moseleyanum is a lowland species from New Guinea and Australia.  Hydnophytum species usually lack spines and have many elongated branches without clypeoli and alveoli.  Their chambers are less complex than those of Myrmecodia.  Note the large entrance hole on the side of this tuber.  Above and left of the entrance hole, a patch of papery dead tissue is peeling away to reveal a new hole.

6.  Hydnophytum formicarum

A very variable and widespread lowland species from Thailand, Malaysia, and Indonesia.  Several different forms varying in size and color are in cultivation.

Hydnophytum formicarum.  A large form from Thailand with entrance holes generally restricted to the underside of the tuber.  The tuber is partially obscured by moss growing up its sides and is larger than it appears.  This plant is twenty-one years old and was the first ant plant I grew from seed.

Hydnophytum cf. formicarum. A plant distinguished by its very broad leaves and smaller tuber with proportionally very large entrance holes.

Hydnophytum cf. formicarum from Belum rainforest, peninsular Malaysia.  This is a dwarf form with brown, flattened tuber and tiny leaves barely as long as those of the Thai form are wide.  Notice the the small entrance hole on the right and pores on the lumpy region at left.

So, that’s six rubiaceous myrmecophytes.  For more Six on Saturday that is perhaps a little less botanically grotesque, head over to The Propagator.

Deciduous hollies

Ilex ‘Sparkleberry’

“Holly” generally brings to mind evergreen species like English holly (Ilex aquifolium) or American holly (Ilex opaca) which are grown for their ornamental spiny foliage as much as for their red berries, but there are also deciduous species with soft leaves that are shed in autumn.  The best evergreen hollies are beautiful, stately trees, but for a punch of winter color, they can’t compete with the deciduous hollies whose heavy crop of berries are never hidden by leaves.

Two species of deciduous hollies are native to the piedmont, and I grow both of them in my garden, along with a commonly cultivated hybrid.  Their leaves are falling now, so they’ll be looking their best until hungry birds eat the berries in late winter.

Ilex verticillata (Winterberry)

Ilex verticillata ‘Winter Red’

I. verticillata thrives best in damp, acidic soil and full sun, but it will tolerate dry soil and part shade.  Dwarf clones of I. verticillata (e.g. ‘Red Sprite’) are great for small gardens, but since we have plenty of space, I planted the full-size ‘Winter Red’ and ‘Winter Gold.’  I. verticillata ‘Winter Red’ will approach 8 feet tall (~2.4 meters) and spread a similar distance with somewhat sprawling branches and root suckers.  Once they have their own roots, I have found that the suckers are easy to transplant, and removing some of them helps the shrub look a little more tidy.

Ilex verticillata ‘Winter Gold’

I. verticillata ‘Winter Gold’ apparently originated as a mutation of ‘Winter Red,’ so apart from the berry color, the two clones are almost identical. At first, I wasn’t very impressed with ‘Winter Gold,’ finding the color somewhat anemic, but over the years it has grown on me.  The golden berries of ‘Winter Gold’ look best in front of dark mulch, while those of ‘Winter Red’ are most dramatic against grass or snow.

All hollies are dioecious, with male and female flowers on separate plants.  Thus, to set berries on female plants like ‘Winter Red’ and ‘Winter Gold,’ you need a male plant that blooms at the same time.  For these late-blooming I. verticillata clones, the best pollinator is I. verticillata ‘Southern Gentleman.’  I have a single ‘Southern Gentleman’ tucked away at the edge of the woods, and it is sufficient to pollinate my three plants of ‘Winter Red’ and one ‘Winter Gold.’

Unfortunately, deer are very fond of the young twigs of I. verticillata which lack the spiky defenses of evergreen holly, and if the hoofed pests consistently nip off the new growth, you will end up with an awkwardly shaped bush and far fewer berries.  If you are in the piedmont and don’t garden behind a deer fence, you’ll need to frequently apply repellents.

Ilex decidua (Possumhaw)

As seen in the comparison picture below, the berries of I. decidua are significantly smaller than those of I. verticillata.  The I. decidua plants that I have seen in the wild have been upright shrubs, generally taller than wide, and the one in my garden has the same shape

I have not planted a male I. decidua, but my female plant sets a good crop of berries every year, probably after pollination by male I. opaca (American holly) trees that grow wild in the woods around our house.  I’m not sure if I. opaca pollen can produce fertile seeds on I. decidua, but I have never found any seedlings that appear to be hybrids.

Comparison of deciduous holly berries:  (left to right) Ilex decidua, Ilex ‘Sparkleberry’, Ilex verticillata ‘Winter Red’, Ilex verticillata ‘Winter Gold’

Ilex ‘Sparkleberry’ (hybrid winterberry)

I. ‘Sparkleberry’ is a hybrid of I. verticillata and a Japanese deciduous holly, I. serrata.     After growing both ‘Sparkleberry’ and I. verticillata ‘Winter Red’ for about ten years, I don’t think the hybrid is an improvement over the native species.  ‘Sparkleberry has a slightly more upright and elegant appearance, but its berries are smaller than those of ‘Winter Red’ (see above), and they don’t tolerate very cold weather, becoming soft and discolored when those of ‘Winter Red’ are still perfect.

In my garden, I. ‘Sparkleberry’ blooms a week or two before late-blooming I. verticillata, so I can’t depend on it being pollinated efficiently by I. ‘Southern Gentleman’.  The best pollinator for I. ‘Sparkleberry’ is I. ‘Apollo,’ a male sibling from the same cross.  I have a single plant of ‘Apollo,’ which I forget about for most of the year, because it is such a nondescript shrub.

Conclusion:  Grow the native species.

Book Review: The Amaryllidaceae of Southern Africa

This book review was also published in the most recent issue of The Bulb Garden, the newsletter of the Pacific Bulb Society.

Graham Duncan, Barbara Jepp, and Leigh Voigt (2017). The Amaryllidaceae of Southern Africa, Umdaus Press, Pretoria, South Africa.

When I first learned of the impending publication of The Amaryllidaceae of Southern Africa, I wondered whether it would be worth purchasing.  After all, a huge amount of information on South African amaryllids is already available without cost at web sites like the PBS wiki or PlantZAfrica.com, a site maintained by the South African National Biodiversity Institute.  However, early descriptions of the book were uniformly positive, and I have hesitated before to purchase an attractive horticulture book, only to discover that its limited print run has sold out and second hand copies are far beyond my budget.  Thus, when the book finally became available, I searched around for the best price and ordered a copy from a distributor in the United Kingdom.  I was not disappointed.

Considered first as a physical artifact, the book is an impressive specimen.  It is printed on heavy, glossy paper bound together with a satin ribbon bookmark.  The endpapers and tough dust jacket are beautifully decorated with line drawings of amaryllid inflorescences and the dust jacket also has a lovely color illustration of Brunsvigia radulosa.  Weighing nearly three kilograms, the book is almost too heavy to read comfortably unless it is placed on a table, and it would certainly not be a good field guide.  However, its physical presence gives the impression that it will outlive the purchaser.

And the content?  This is the finest botany/horticulture book I have read in a long time.  As most advertisements and descriptions indicate, the book’s main selling point is its botanical illustrations, which represent almost forty-five years of work by Barbara Jeppe and her daughter Leigh Voigt.  The book covers every single species in all of the amaryllid genera found in Southern Africa, a region encompassing both the summer- and winter-rainfall regions of South Africa, Swaziland, Lesotho, Namibia, and Botswana.  Each full-color botanical illustration shows the bulb, foliage, flowers, and fruit.  A notation at the bottom of each illustration indicates its scale as a percentage of life-size, making it easy to determine the actual size of the flowers.  In my browsing of the book, I found only a couple of species illustrated with older paintings or lacking an illustration, because no living material was available to the artists.

All species, including those few with no illustration, have a detailed description written by Graham Duncan, the curator of the indigenous bulb collection at Kirstenbosch National Botanical Garden in Cape Town, South Africa.  In addition to a physical description, Duncan’s text includes a brief history of the species (including provenance of the illustrated plant), flowering period, distribution and habitat, conservation status, and cultivation notes.  This latter section will probably be of great interest to bulb enthusiasts and gardeners.  If, like me, you sometimes have trouble remembering which parts of South Africa receive winter rainfall and which months in the southern hemisphere correspond to our northern hemisphere growing season, you’ll be pleased to see that the cultivation instructions usually state exactly when a species should be watered in terms of season, not months of the year.

The various genera and species are presented in alphabetical order, making it easy to find a species of interest.  Each genus is introduced with a more general description that includes numerous color photographs, many of them showing plants in habitat. Introductory material at the front of the book includes sections on amaryllid biogeography and survival strategies.  These sections were particularly interesting to me, because I find that much of the fun of growing exotic plants lies in learning about their biology, evolution, and habitat.

The end of the book includes a key to all genera and species, a glossary, and a more detailed cultivation guide split into sections for growers in the northern and southern hemispheres.  The northern hemisphere guide includes helpful instructions for acclimatizing bulbs imported from South Africa, as well as lists of recommended species for cultivation outside.  These lists are, I think, the least useful aspect of the book for growers in North America.  The cultivation guide was clearly written with the United Kingdom in mind, and there is no obvious way to translate the “hardy” and “half-hardy” categories into USDA climate zones.  In some cases, the cultivation guide seems too conservative, stating that Nerine bowdenii is “the only fully hardy summer-rainfall amaryllid” and that Crinum bulbispermum is merely “frost-hardy.”  With these minor quibbles, though, I am still impressed by the cultivation guide and think that its information on propagation, pests and diseases, and potting media will be of great utility to North American growers.

For me, the biggest surprise in this book has been learning just how many absolutely gorgeous amaryllids there are that do not seem to be in cultivation in the United States.  Perhaps the list of seed and bulb suppliers at the end of the book will offer me the opportunity to test those instructions for acclimatizing imports.

Brief intermission

I have been away at a conference in Washington, DC.  Until I have a chance to get back out into the  garden, please enjoy this portrait with significant horticultural content that I saw while touring the National Gallery of Art during my lunch break.

Rubens Peale with a Geranium was painted by the human subject’s older brother, Rembrandt Peale, in 1801.   According to the story attached to the painting, the botanical subject was grown by Rubens Peale and was the first of its kind to bloom in North America.

“Painted in Philadelphia, the work could be described as a double portrait because the geranium, reputed to be the first specimen of this exotic plant ever grown in the New World, is as lovingly portrayed as the painter’s brother is…Combining firm, clear drawing, carefully modulated color, and an intense devotion to detail, twenty-three-year-old Rembrandt Peale produced an eloquent expression of his family’s philosophical orientation.”  Source

 

Abutilon megapotamicum

Abutilon megapotamicum is another plant whose presence in my garden is a direct result of a trip to J.C. Raulston Arboretum (see also, Fatsia japonica).  I’m not proud of the fact that I ignored Abutilons for a long time because their common name, flowering maple, was so unappealing.  There’s nothing wrong with maples, but there’s nothing exotic and exciting about them either.  Calling a beautiful subtropical plant “flowering maple” effectively rendered it dull and uninteresting to me.

My opinion was changed by a large A. megapotamicum plant at Raulston.  Hummingbirds and Me:  we all love bell shaped flowers in bright orange-red-yellow, and A. megapotamicum fits the bill.  Here was a gorgeous, tropical-looking shrub whose size strongly suggested that it was winter-hardy, not a recently planted annual.  I decided to try it in my garden, too.

The origins of A. megapotamicum are somewhat mysterious.  Most sources agree that it originates in southern South America–Brazil, Argentina, Uruguay–but I haven’t been able to find any detailed information about its habitat or ecology.  It is widely cultivated for its flowers and widely naturalized in the tropics and subtropics, so perhaps it is one of those species that have been spread so widely by humans that their origins have been obscured.

Apart from the lovely flowers, A. megapotamicum is not a particularly impressive shrub. It has a semi-scandent habit with long, thin, poorly branched stems that have a tendency to use other plants for support.  The flowers are somewhat attractive to hummingbirds, but I haven’t noticed it attracting any insects or other animals.  So, not a particularly good plant for wildlife, but worth including in the garden for its very long flowering period.  My plant blooms from just after the last frost until well into winter, with a short break during the hottest part of summer.  Last winter, I even had a couple of flowers in January during a mild spell.

I planted A. megapotamicum in spring of 2016, so it has only been through one winter so far.  Last winter was mild, but the lowest temperature was about 12 F (-11 C), and we had at least one good snowfall.  The plant showed no damage above 20 F and only partial leaf drop below 20.  I’m hoping that it is well enough established now that it will sprout from the roots if damaged by colder weather in 2017/2018.

My lone clone of A. megapotamicum has not produced any seed, but cuttings seem very easy to root.  I cut several stem tips as insurance last winter, wrapped them in damp paper towels, and stored them in a plastic bag until I had time to pot them up.  When I remembered them a couple of weeks later, they had rooted into the paper towels.